John Gill Commentary 2 Samuel 15:27

"The king said also unto Zadok the priest, Art thou [not] a seer? return into the city in peace, and your two sons with you, Ahimaaz thy son, and Jonathan the son of Abiathar." — 2 Samuel 15:27 (ASV)

And the king said to Zadok the priest, [are you not] you a
seer ?
&c.] A prophet, as well as a priest; see (1 Samuel 9:9) ; or a seeing, knowing, man; one that can penetrate into men and things, and so might be of more service to David at Jerusalem than with him: wherefore he said to him,

return into the city in peace ;
to the city of Jerusalem with peace, quietness, and satisfaction of mind; where he doubted not, at least hoped and wished, he would be in safety and prosperity, being one of the Lord's priests:

and your two sons with you, Ahimaaz your son, and Jonathan the son of
Abiathar ;
the one was of the line of Eleazar, and the other of the line of Ithamar.