If Jesus died for our sins…why should we need to be baptized for the forgiveness of our sins (besides the fact of it being a command)?
I do not mean to be facetious, but the simple answer is “Because God said so.” If God tells us to do something, it is not required that he tell us why he wants us to do it, or to explain how it is consistent with other things he has said. It is our job to trust and obey. If we find the command to be not “logical” based on some sort of human logic, this would not give us justification to not obey the command. Of course, you are acknowledging my point by the very way that you ask it.
But… There is nothing wrong with trying to use human reasoning, based on biblical truths, to explain the “why” of baptism. I will answer the question by asking another. Why, when he put the mud in the eyes of the man born blind, did Jesus tell him to wash in the Pool of Siloam? I think you can guess.
And why did Elisha have Naaman go all the way to the River Jordan to dip in it seven times in order to be cleansed of leprosy? Was this for God’s sake, or was it for the sake of Naaman? I think you can guess.
OK. Now another question. Why does God ask people who have committed their lives together to go through something like a marriage–to have a ceremony marking the transition from not being married to being married? Because we need to know when we pass from not married to married. Similarly, we, as humans, need to know when we have passed from not saved to saved–from not forgiven to forgiven.
The fact that Jesus died for our sins does not mean that everyone is forgiven of their sins. Apparently, the mere fact that Jesus died for our sins does not automatically mean that every person is saved. Some sort of response is required. God asks us to some things in order to be saved. In John 6:28-29 Jesus is asked what works we must do (presumably to be saved) and he said that we must believe in the one he has sent. When asked what one must do in response to the death of Jesus, Peter told the crowd to repent and be baptized (Acts 2:36-39). Based on the death of Jesus, all of us have the potential to be forgiven of our sins, but God asks us to believe, repent and be baptized. It is at the point of baptism that the forgiveness occurs, as is apparent from Acts 2:38 and Romans 6:3-7. The fact that the water of baptism points toward the cleansing from our sins is also in play here. That water would be a factor in salvation is prophesied many times in the Old Testament (Zechariah 13:1-2, Ezekiel 36:24-27 for example).