1 Corinthians 12:3:

Wherefore I give you to understand, that no man speaking by the Spirit of God calleth Jesus accursed: and that no man can say that Jesus is the Lord, but by the Holy Ghost.

See also:

What Romans 8:9 Really Means
Objection: We Should Never Teach that Jesus Was Cursed Because No One Speaking by the Holy Spirit Can Call Jesus Cursed (1 Corinthians 12:3)