Contradiction with James 1:19
James 1:19 implies that one should be swift to hear and slow to speak, which highlights patience over the promptness praised in Proverbs 15:23.
James 1:19: Wherefore, my beloved brethren, let every man be swift to hear, slow to speak, slow to wrath:
Contradiction with Proverbs 17:27
Proverbs 17:27 suggests that a person of knowledge uses words with restraint, whereas Proverbs 15:23 praises a timely word possibly implying more frequent verbal engagement.
Proverbs 17:27: He that hath knowledge spareth his words: [and] a man of understanding is of an excellent spirit. [an...: or, a cool]
Contradiction with Ecclesiastes 3:7
Ecclesiastes 3:7 notes that there is a time to be silent, which contrasts with Proverbs 15:23's emphasis on the joy in providing a timely word.
Ecclesiastes 3:7: A time to rend, and a time to sew; a time to keep silence, and a time to speak;
Contradiction with Proverbs 21:23
Proverbs 21:23 advises guarding one's mouth to avoid trouble, contradicting the notion that speaking timely always brings joy as stated in Proverbs 15:23.
Proverbs 21:23: Whoso keepeth his mouth and his tongue keepeth his soul from troubles.
Contradiction with James 3:8
James 3:8 warns about the uncontrollable nature of the tongue, implying that speaking (even timely) can be dangerous, contrary to the positive outcome in Proverbs 15:23.
James 3:8: But the tongue can no man tame; [it is] an unruly evil, full of deadly poison.