Acts 10

 I find it interesting that Peter - 

"...saw heaven opened, and a certain vessel descending unto him, as it had been a great sheet knit at the four corners, and let down to the earth:

12 Wherein were all manner of fourfooted beasts of the earth, and wild beasts, and creeping things, and fowls of the air.

13 And there came a voice to him, Rise, Peter; kill, and eat.

14 But Peter said, Not so, Lord; for I have never eaten any thing that is common or unclean.

15 And the voice spake unto him again the second time, What God hath cleansed, that call not thou common.

16 This was done thrice: and the vessel was received up again into heaven."  (Acts 10:11–16)

The interesting part that it was so important that tthe voice said it "thrice".  There is much meaning in "three".