Deuteronomy 18:21
And if thou say in thine heart, How shall we know the word which the Lord hath not spoken?
Cross-reference
1 John 4:1–3
Parallel
1 John 4:1-3 directly instructs testing spirits to see if they are from God — a clear parallel to testing prophets.
Revelation 2:2
Parallel
Revelation 2:2 commends testing false apostles — echoes the same call to discern true from false messengers.