Contradiction with 2 Samuel 17:14
This verse shows that the Lord had determined to frustrate the good advice of Ahithophel, while 2 Samuel 17:26 is about David and Israel in the battle preparation.
2 Samuel 17:14: And Absalom and all the men of Israel said, The counsel of Hushai the Archite [is] better than the counsel of Ahithophel. For the LORD had appointed to defeat the good counsel of Ahithophel, to the intent that the LORD might bring evil upon Absalom. [appointed: Heb. commanded]
Contradiction with 2 Samuel 17:15
Provides information of Ahithophel's advice and its communication, contrasting with the focus on physical troop location in 2 Samuel 17:26.
2 Samuel 17:15: Then said Hushai unto Zadok and to Abiathar the priests, Thus and thus did Ahithophel counsel Absalom and the elders of Israel; and thus and thus have I counselled.
Contradiction with 2 Samuel 17:23
It narrates Ahithophel's response to his advice not being followed, which contrasts with the strategic movements in 2 Samuel 17:26.
2 Samuel 17:23: And when Ahithophel saw that his counsel was not followed, he saddled [his] ass, and arose, and gat him home to his house, to his city, and put his household in order, and hanged himself, and died, and was buried in the sepulchre of his father. [followed: Heb. done] [put his...: Heb. gave charge concerning his house]