Contradiction with Leviticus 11:10
This verse lists unclean animals from the waters, which would include many types of fish, contradicting the invitation to eat without mention of dietary laws in John 21:12.
Leviticus 11:10: And all that have not fins and scales in the seas, and in the rivers, of all that move in the waters, and of any living thing which [is] in the waters, they [shall be] an abomination unto you:
Contradiction with Acts 10:14
Peter initially resists eating unclean animals shown to him in a vision, contradicting the acceptance of eating whatever is provided without question as seen in John 21:12.
Acts 10:14: But Peter said, Not so, Lord; for I have never eaten any thing that is common or unclean.
Contradiction with Romans 14:21
Advocates for not doing anything that might cause a fellow believer to stumble, contrasting with the direct invitation to eat in John 21:12 without consideration for others' beliefs.
Romans 14:21: [It is] good neither to eat flesh, nor to drink wine, nor [any thing] whereby thy brother stumbleth, or is offended, or is made weak.
Contradiction with 1 Corinthians 8:13
Paul states he would avoid eating meat if it causes a brother to stumble, which contradicts the clear invitation to eat with Jesus in John 21:12 without such concern.
1 Corinthians 8:13: Wherefore, if meat make my brother to offend, I will eat no flesh while the world standeth, lest I make my brother to offend.
Contradiction with Colossians 2:16
Advises against being judged on dietary practices, which contrasts with the straightforward action of eating together described in John 21:12.
Colossians 2:16: Let no man therefore judge you in meat, or in drink, or in respect of an holyday, or of the new moon, or of the sabbath [days]: [in meat...: or, for eating and drinking] [respect: or, part]