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. 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.
Hushai told Zadok and Abiathar both what Ahithophel had advised Absalom and the elders of Israel and what counter-advice he himself had given. He used the priests as messengers to warn David to cross the Jordan that very night. The urgency was because Absalom was seeking David's life. His counsel succeeded in its aim by holding Absalom back and thereby winning time for David to get across the Jordan to Mahanaim before Absalom could follow with his large but undisciplined army.