Contradiction with Matthew 7:7
It suggests asking and it shall be given, which implies all prayers are answered, differing from any notion of the conditional hearing in 2 Chronicles 6:21.
Matthew 7:7: Ask, and it shall be given you; seek, and ye shall find; knock, and it shall be opened unto you:
Contradiction with James 4:3
States that some prayers are not answered because they are asked amiss, contradicting the idea of simply hearing prayers as 2 Chronicles 6:21 implies.
James 4:3: Ye ask, and receive not, because ye ask amiss, that ye may consume [it] upon your lusts. [lusts: or, pleasures]
Contradiction with John 9:31
Suggests that God does not listen to sinners, which contrasts with the notion of God hearing all prayers as mentioned in 2 Chronicles 6:21.
John 9:31: Now we know that God heareth not sinners: but if any man be a worshipper of God, and doeth his will, him he heareth.
Contradiction with Proverbs 28:9
States that one who turns away from the law, even their prayer is an abomination, contrasting with the unconditional hearing aspect of 2 Chronicles 6:21.
Proverbs 28:9: He that turneth away his ear from hearing the law, even his prayer [shall be] abomination.
Contradiction with Isaiah 1:15
Indicates that God will not hear prayers when hands are full of blood, contradicting the inclusivity of prayer hearing in 2 Chronicles 6:21.
Isaiah 1:15: And when ye spread forth your hands, I will hide mine eyes from you: yea, when ye make many prayers, I will not hear: your hands are full of blood. [make...: Heb. multiply prayer] [blood: Heb. bloods]