Contradiction with 2 Samuel 24:18-24
The account of purchasing the threshing floor differs in detail regarding the seller's title, name, and the interaction between David and the seller.
2 Samuel 24:18-24: And Gad came that day to David, and said unto him, Go up, rear an altar unto the LORD in the threshingfloor of Araunah the Jebusite. [Araunah: Heb. Araniah]
Contradiction with Exodus 20:13
1 Chronicles 21 involves actions leading to a deadly plague, conflicting with the commandment "Thou shalt not kill."
Exodus 20:13: Thou shalt not kill.
Contradiction with Numbers 23:19
This verse asserts that God does not change His mind, while 1 Chronicles 21 shows God changing His course in response to David's actions.
Numbers 23:19: God [is] not a man, that he should lie; neither the son of man, that he should repent: hath he said, and shall he not do [it]? or hath he spoken, and shall he not make it good?
Contradiction with Genesis 22:2
God asks Abraham to sacrifice Isaac, differing from the mercy shown when David builds an altar in response to the angel's message.
Genesis 22:2: And he said, Take now thy son, thine only [son] Isaac, whom thou lovest, and get thee into the land of Moriah; and offer him there for a burnt offering upon one of the mountains which I will tell thee of.