Contradiction with Matthew 6:3
This verse advises not to let your left hand know what your right hand is doing when giving, which contradicts the emphasis on preparedness for boasting about giving in 2 Corinthians 9:4.
Matthew 6:3: But when thou doest alms, let not thy left hand know what thy right hand doeth:
Contradiction with Proverbs 19:17
This verse implies that giving to the poor is lending to the Lord and will be repaid, focusing on quiet, divine recompense as opposed to the public boasting implied in 2 Corinthians 9:4.
Proverbs 19:17: He that hath pity upon the poor lendeth unto the LORD; and that which he hath given will he pay him again. [that which...: or, his deed]
Contradiction with Matthew 6:1
This verse warns against practicing righteousness before others to be seen by them, contrasting with the anticipation of boasting in 2 Corinthians 9:4.
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]