Are not Zadok and Abiathar the priests with you there? So whatever you hear from the king’s house, tell it to Zadok and Abiathar the priests.
Nothing, it seems, appeared to David more threatening in Absalom's plot than that Ahithophel was in it; for one good head, in such a design, is worth a thousand good hands. Absalom was himself no politician, but he had got one entirely in his interest that was, and would be the more dangerous because he had been all along acquainted with David's counsels and affairs...
Commenting on 2 Samuel 15:31-37
And hast thou not there with thee Zadok and Abiathar the priests?.... To assist in forming schemes directly opposite to Ahithophel's, or to whom he could communicate the secrets of Absalom's court: therefore it shall be that what thing soever thou shalt hear out of the king's house; Absalom's, who had now, at possession of the house and palace of David: thou shalt tell it...
2Sa 15:35-36 David then commissioned him to communicate to the priests Zadok and Abiathar all that he should hear of the king’s house, and send word to him through their sons.
Commenting on 2 Samuel 15:35-36