Contradiction with Proverbs 28:9
This verse suggests that if one turns away from hearing the law, even their prayer is an abomination, which contradicts the idea of calling upon God in trouble and being delivered in Psalms 50:15.
Proverbs 28:9: He that turneth away his ear from hearing the law, even his prayer [shall be] abomination.
Contradiction with Isaiah 1:15
This verse indicates that when hands are full of blood, God will hide His eyes and not listen to prayers, in contrast to Psalms 50:15, which promises deliverance when called upon.
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]
Contradiction with John 9:31
This verse states God does not hear sinners, which opposes Psalms 50:15 by implying that only the righteous can expect help when calling on God.
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 James 4:3
This verse notes that prayers can go unanswered if asked amiss, contrasting with the assurance of deliverance found in Psalms 50:15.
James 4:3: Ye ask, and receive not, because ye ask amiss, that ye may consume [it] upon your lusts. [lusts: or, pleasures]