He saw heaven opened1 and something like a large sheet being let down to earth by its four corners.
References for Acts 10:11
It contained all kinds of four-footed animals, as well as reptiles of the earth and birds of the air.
Then a voice told him, "Get up, Peter. Kill and eat."
"Surely not, Lord!"2 Peter replied. "I have never eaten anything impure or unclean."3
References for Acts 10:14
The voice spoke to him a second time, "Do not call anything impure that God has made clean."4
References for Acts 10:15
This happened three times, and immediately the sheet was taken back to heaven.