Contradiction with Jeremiah 31:34
Hebrews 10:17 cites this verse, which states that God will forgive and forget sins, but it is taken as consistent rather than contradictory. However, in Jeremiah 31:34 the emphasis is on a future act.
Jeremiah 31:34: And they shall teach no more every man his neighbour, and every man his brother, saying, Know the LORD: for they shall all know me, from the least of them unto the greatest of them, saith the LORD: for I will forgive their iniquity, and I will remember their sin no more.
Contradiction with Exodus 34:7
This verse mentions that God will not clear the guilty and visits the iniquity of fathers upon children, which seems contrary to forgetting sins.
Exodus 34:7: Keeping mercy for thousands, forgiving iniquity and transgression and sin, and that will by no means clear [the guilty]; visiting the iniquity of the fathers upon the children, and upon the children's children, unto the third and to the fourth [generation].
Contradiction with Numbers 14:18
Similar to Exodus 34:7, it talks about God visiting iniquity, suggesting a remembrance of sins.
Numbers 14:18: The LORD [is] longsuffering, and of great mercy, forgiving iniquity and transgression, and by no means clearing [the guilty], visiting the iniquity of the fathers upon the children unto the third and fourth [generation].
Contradiction with 1 Samuel 15:2-3
God instructs Saul to punish the Amalekites for past sins, indicating a remembrance of those sins.
1 Samuel 15:2-3: Thus saith the LORD of hosts, I remember [that] which Amalek did to Israel, how he laid [wait] for him in the way, when he came up from Egypt.
Contradiction with Ezekiel 18:24
This verse states that if a righteous person turns from righteousness and commits iniquity, all their former righteousness will not be remembered, suggesting conditional remembrance of past sins.
Ezekiel 18:24: But when the righteous turneth away from his righteousness, and committeth iniquity, [and] doeth according to all the abominations that the wicked [man] doeth, shall he live? All his righteousness that he hath done shall not be mentioned: in his trespass that he hath trespassed, and in his sin that he hath sinned, in them shall he die.
Contradiction with Amos 8:7
God swears by the pride of Jacob that He will not forget the works of Israel, implying remembrance of their actions.
Amos 8:7: The LORD hath sworn by the excellency of Jacob, Surely I will never forget any of their works.