Here is some information on the reasoning. Hope this helps.

Peter's vision of a sheet with animals
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According to the Acts of the Apostles, chapter 10, Saint Peter had a vision of a vessel (Greek: σκεῦός, skeuos; "a certain vessel descending upon him, as it had been a great sheet knit at the four corners") full of animals being lowered from heaven (Acts 10:11). A voice from heaven told Peter to kill and eat, but since the vessel (or sheet, ὀθόνη, othonē) contained unclean animals, Peter declined. The command was repeated two more times, along with the voice saying, "What God hath made clean, that call not thou common" (verse 15) and then the vessel was taken back to heaven (verse 16).

At this point in the narrative, messengers sent from Cornelius the Centurion arrive and urge Peter to go with them. He does so, and mentions the vision as he speaks to Cornelius, saying "God hath shewed me that I should not call any man common or unclean" (Acts 10:28). Peter related the vision again in Acts 11:4-9.

Interpretation
Simon J. Kistemaker suggests that the lesson God taught Peter in this vision is that "God has removed the barriers he once erected to separate his people from the surrounding nations."[1]:378 Kistemaker argues that it means Peter has to accept Gentile believers as full members of the Christian Church, but also that God has made all animals clean, so that "Peter with his fellow Jewish Christians can disregard the food laws that have been observed since the days of Moses."[1]:380 Albert Mohler, President of Southern Seminary, writes:[2]

As the Book of Acts makes clear, Christians are not obligated to follow this holiness code. This is made clear in Peter's vision in Acts 10:15. Peter is told, 'What God has made clean, do not call common.' In other words, there is no kosher code for Christians. Christians are not concerned with eating kosher foods and avoiding all others. That part of the law is no longer binding, and Christians can enjoy shrimp and pork with no injury to conscience.

Luke Timothy Johnson and Daniel J. Harrington write that this episode heralds a radical change in Peter's "identity as a member of God's people,"[3]:187- but also that "the implication is that all things God created are declared clean by him, and are not affected by human discriminations."[3]:184
https://en.wikipedia.org/wiki/Peter%27s_vision_of_a_sheet_with_animals