Should we baptize infants or others who are unable to decide for themselves?

The passages you cited are frequently quoted by proponents of infant baptism, however, their misuse of these texts is a classic example of the error of eisegetical interpretation of scripture. Eisegetical interpretation is a process of seeking biblical support for pre-existing views rather than allowing the biblical text to explain itself naturally. This method is wrong because it does not allow the text to teach us objectively.

The correct form of biblical interpretation is exegetical interpretation, which involves studying the text without preconceived views so that the truth of scripture is impressed upon our heart without bias. When we study the two passages you mentioned in your question exegetically, we find that neither is teaching on the subject of baptism explicitly nor do these passages imply the conclusion your pastor (and others) have made concerning infant baptism. 

First, consider the passage in Luke:

Luke 18:15  And they were bringing even their babies to Him so that He would touch them, but when the disciples saw it, they began rebuking them. 
Luke 18:16 But Jesus called for them, saying, “Permit the children to come to Me, and do not hinder them, for the kingdom of God belongs to such as these.
Luke 18:17 “Truly I say to you, whoever does not receive the kingdom of God like a child will not enter it at all.”

The women were bringing infants to Jesus (presumably for a blessing). The disciples felt this behavior was inappropriate, probably because they didn’t believe Jesus should be burdened with concerns that were beneath His purpose and importance.

Notice in v.15 the women were bringing infants since the Greek word for “babies” is brephos, which is the word for infant (i.e., a child too young to walk). Nevertheless, when Jesus responds to the disciples, he uses a different Greek word. Jesus says to let the “children” to come to Him. The Greek word for children is paidion, which generally refers to a school-age child. This distinction is important because it tells us that Jesus is not specifically addressing the issue of infants, which were being brought to Him (much less was He speaking about the topic of baptism). 

Then in v.17 we come to understand why Jesus desires that children be allowed to physically come to Him. Jesus wishes to use the idea of children coming to visit Him physically as a metaphor for humanity coming to Him spiritually. Jesus says that a child coming to Him is a model or picture for how every heart comes to saving faith. A child comes to Jesus in joy, with an expectation of a warm reception, without a sense of self-worth. A child brings nothing of worth to Jesus and makes no pay payment. Finally, a child trusts an adult without wavering. 

These are the common characteristic of true saving faith at any age. Every believer must humble themself and believe they have nothing to offer Christ nor can they make any payment on their own behalf. They brings only joyful expectation that Jesus will receive them warmly and they holds this trust without doubt or wavering. This is “child-like” saving faith.

As we understand Jesus’ true purpose in comparing faith to children, we come to realize this passage offers no support for the practice of infant baptism. In fact, it says nothing at all about the subject whatsoever. Jesus spoke only of children, not infants, and His reference to children was only as a metaphor for saving faith. To draw any conclusion regarding the proper manner of baptism from this passage requires eisegetical manipulation of the text and is not a valid interpretation. 

Looking at the second passage in Acts, we find:

Acts 16:27 When the jailer awoke and saw the prison doors opened, he drew his sword and was about to kill himself, supposing that the prisoners had escaped. 
Acts 16:28 But Paul cried out with a loud voice, saying, “Do not harm yourself, for we are all here!” 
Acts 16:29 And he called for lights and rushed in, and trembling with fear he fell down before Paul and Silas, 
Acts 16:30 and after he brought them out, he said, “Sirs, what must I do to be saved?” 
Acts 16:31 They said, “Believe in the Lord Jesus, and you will be saved, you and your household.” 
Acts 16:32 And they spoke the word of the Lord to him together with all who were in his house. 
Acts 16:33 And he took them that very hour of the night and washed their wounds, and immediately he was baptized, he and all his household.
Acts 16:34 And he brought them into his house and set food before them, and rejoiced greatly, having believed in God with his whole household. 

In response to the earthquake, Paul’s jailer comes to a moment of repentance and seeks salvation in Paul’s God. Paul, under the inspiration of the Holy Spirit, instructs the jailer that if he believes in the Lord Jesus Christ he would be saved along with his household. Hearing Paul’s instructions the jailer believed, and as Paul promised, the jailer's entire household followed suit into faith resulting in the entire household being baptized and rejoicing. 

Once again, this passage teaches nothing specifically about the issue of infant baptism. First, no ages for the members of the household are ever mentioned in this passage, so it is entirely possible that everyone in the jailer's household was older individuals. Many households have no infants. Without a specific mention of an infant receiving baptism, we simply cannot draw any conclusion from this passage. 

Furthermore, the events in this passage are clearly supernatural in all respects, and therefore this scene is not a suitable prescription for common practice within the church. Believers do not routinely enter into faith as the result of supernatural earthquakes, nor do all believers receive their proclamation of the Gospel from the Apostle Paul himself. Similarly, the Lord does not promise to all believers that when one person believes that his or her entire household will always follow suit. 

These unique and specific details confirm that this moment was not a prescription for how all believers should expect to see the Lord working. Rather, this is a description of how one person’s experience transpired. As such, we can draw no conclusions from the story concerning the normative experience in the church.

Therefore, even if one assumed that the jailer’s household included an infant who received baptism, we still cannot presume that this serves as a pattern for all believers. Such a conclusion is an eisegetical misinterpretation of scripture. The only proper and reasonable interpretation we may make concerning the moment in Acts 16 is that the Lord chose to do something unique and powerful through this jailer’s family in order to authenticate and magnify Paul’s apostolic ministry. Nevertheless, this moment says nothing about common practices in the church. 

Besides these wrongly interpreted passages, the Bible does provide teaching on the proper practice of baptism in passages specifically addressing the issue. 

First, the Lord Himself modeled the proper manner of water baptism when He received His own baptism under John:

Mark 1:9  In those days Jesus came from Nazareth in Galilee and was baptized by John in the Jordan. 
Mark 1:10 Immediately coming up out of the water, He saw the heavens opening, and the Spirit like a dove descending upon Him; 

The Bible tells us specifically that Jesus was baptized as an adult and by immersion under water. The Bible reports that Jesus was 30 years of age when He received baptism, not an infant. If infancy was the appropriate moment in life to receive water baptism, then we would have expected our Lord to have modeled this pattern for us by being baptized as an infant Himself. Instead, the Lord waited until He came into His earthly ministry as an adult to be baptized.

Secondly, we are told explicitly that after He was baptized, Jesus came “up out of the water.” This description precludes the possibility that Jesus received water baptism through a sprinkling or pouring of water over the head (which is commonly practiced among those who advocate infant baptism). 

Instead, the text clearly indicates that Jesus was immersed in the river such that He came “up out of the water” at the conclusion of the baptism. Such explicit language demonstrates clearly how the Lord practiced water baptism, so based on this passage we must conclude that the proper model for water baptism is immersion by those who may freely enter into the water (i.e., someone old enough to enter on their own, not an infant).   

Furthermore, the theology of baptism (i.e., it’s underlying meaning and purpose) must dictate our practice. The form of a ritual must support the ritual’s message and purpose, and when we consult the Bible’s teaching on the theology of baptism, we’re led to a very specific form. 
Paul describes the theology of baptism clearly in Colossians 2 and 1Corinthians 15:

Col. 2:9 For in Him all the fullness of Deity dwells in bodily form, 
Col. 2:10 and in Him you have been made complete, and He is the head over all rule and authority; 
Col. 2:11 and in Him you were also circumcised with a circumcision made without hands, in the removal of the body of the flesh by the circumcision of Christ; 
Col. 2:12 having been buried with Him in baptism, in which you were also raised up with Him through faith in the working of God, who raised Him from the dead. 
Col. 2:13 When you were dead in your transgressions and the uncircumcision of your flesh, He made you alive together with Him, having forgiven us all our transgressions, 
Col. 2:14 having canceled out the certificate of debt consisting of decrees against us, which was hostile to us; and He has taken it out of the way, having nailed it to the cross. 
1Cor. 15:29 Otherwise, what will those do who are baptized for the dead? If the dead are not raised at all, why then are they baptized for them? 

In Colossians, Paul teaches that Christ died on our behalf to pay our debt for sin. Through faith in His sacrifice, we are credited with His righteousness, and therefore we may share in His eternal life. He took our condemnation under the decrees of the Law and “nailed it to the cross” by paying the price the Law required for our sin.

Paul then says our water baptism pictures our dying with Christ and our hope for resurrection. How can water baptism convey such important theology? Simply put, the water of our baptism represents the grave, so that by going under the water we picture our burial with Christ, and then by our “coming up out of the water” we picture our hope in a future resurrection into an eternal body. 

Obviously, this important message would be lost if the ritual of water baptism took a form other than the one Jesus modeled. For example, sprinkling water on a body does not communicate burial and resurrection. Likewise, an infant (or even a young child) being “washed” with water by an adult cannot substitute for a personal identification in the death and resurrection of Jesus Christ, which baptism is intended to picture. Therefore, to wet an infant and call it “baptism” destroys the very meaning and purpose of the ritual according to scripture. 

Finally, in 1Corinthians 15 Paul explains that the baptism for the [resurrection of the] dead is accomplished because we hold that believers will be resurrected into eternal life. Therefore, Paul asks why the church in Corinth was willing to practice water baptism if the church was doubting in the doctrine of resurrection? Paul’s commentary reaffirms that water baptism is intended to picture the death and resurrection of a body.

In our experience pastors and teachers who defend infant baptism do so out of a desire to support denominational traditions. They search the Bible for passages that appear to support their church’s preconceived doctrines because breaking free from their denominational viewpoint brings career and personal risks. 

Nevertheless, we encourage all men and women to seek agreement with the word of God, even if it comes at the expense of denominational fellowship or career progression. When we stand before our Lord at our judgment, we will be judged according to our obedience to the word, not by our loyalty to denominations. 

As Jesus said:

Luke 11:27  While Jesus was saying these things, one of the women in the crowd raised her voice and said to Him, “Blessed is the womb that bore You and the breasts at which You nursed.” 
Luke 11:28 But He said, “On the contrary, blessed are those who hear the word of God and observe it.”
 

Scripture quotations taken from the (NASB®) New American Standard Bible®, Copyright © 1995, 2020 by The Lockman Foundation. Used by permission. All rights reserved. www.lockman.org