2 Samuel 15:27
The king said also unto Zadok the priest, Art not thou a seer? return into the city in peace, and your two sons with you, Ahimaaz thy son, and Jonathan the son of Abiathar. The king said also unto Zadok the priest, Art not thou a seer? return into the city in peace, and your two sons with you, Ahimaaz thy son, and Jonathan the son of Abiathar.
David sends Zadok the priest back into the city in peace, together with Abiathar and their two sons, Ahimaaz the son of Zadok and Jonathan the son of Abiathar. In calling Zadok a seer he identifies him as a man appointed by God to instruct the people. With them David sends the ark back to its proper place in Jerusalem, rather than keeping it with him to strengthen his claim or to protect himself. This shows reverence for the ark and willingness to submit to God's judgment, awaiting God's decision about whether he will be restored.
The priests are to remain in the city to do him good service by learning the movements and purposes of the rebels. They are to communicate what they learn secretly to the king through their sons, while David waits in the plain of the wilderness until word comes from them to inform him.