Contradiction with 1 Samuel 16:19
Contradicts how Saul is unaware of David, as Saul already sent for David to attend him.
1 Samuel 16:19: Wherefore Saul sent messengers unto Jesse, and said, Send me David thy son, which [is] with the sheep.
Contradiction with 1 Samuel 17:58
Saul acts as if he does not recognize David, contradicting prior familiarity from 1 Samuel 16.
1 Samuel 17:58: And Saul said to him, Whose son [art] thou, [thou] young man? And David answered, I [am] the son of thy servant Jesse the Bethlehemite.
Contradiction with 2 Samuel 21:19
Suggests that Elhanan killed Goliath, contradicting David being called to Saul because of his words against Goliath.
2 Samuel 21:19: And there was again a battle in Gob with the Philistines, where Elhanan the son of Jaareoregim, a Bethlehemite, slew [the brother of] Goliath the Gittite, the staff of whose spear [was] like a weaver's beam. [Jaareoregim: or, Jair]