Contradiction with Matthew 6:1
It advises to not do alms before men to be seen by them, while 2 Corinthians 9:9 emphasizes giving publicly.
Matthew 6:1: Take heed that ye do not your alms before men, to be seen of them: otherwise ye have no reward of your Father which is in heaven. [alms: or, righteousness] [of your: or, with your]
Contradiction with Proverbs 28:27
States that giving to the poor will not lead to lack, potentially conflicting with the trials that come despite righteousness in 2 Corinthians 9:9.
Proverbs 28:27: He that giveth unto the poor shall not lack: but he that hideth his eyes shall have many a curse.
Contradiction with Ecclesiastes 11:1
Suggests casting your bread upon the waters shall return after many days, which might contradict 2 Corinthians 9:9 by implying eventual earthly return rather than eternal righteousness.
Ecclesiastes 11:1: Cast thy bread upon the waters: for thou shalt find it after many days. [upon...: Heb. upon the face of the waters]