1 Kings 1:34

Let Zadok the priest and Nathan the prophet anoint him That is, say the Jews, one of them poured out the oil, and the other anointed his head, drawing a circle round about it with oil, according to their maxim that their kings were anointed in the form of a crown, to denote their delegation to the royal dignity. It is of more importance to observe, that this unction signified not only the designation of the person anointed to his office, but the gifts and graces which were necessary to qualify him for it, and which, seeking them sincerely of God, he might expect to receive. “We do not find,” says Henry, “that Abiathar pretended to anoint Adonijah: he was made king by a feast, not by unction. Whom God calls, he will qualify, which was signified by the anointing: usurpers had it not. Christ signifies anointed, and he is the king whom God hath set upon his holy hill of Zion, according to the decree, Psalms 2:6. Christians, also, are made to our God, and by him, kings, and they have an unction from the Holy One, 1 John 2:20.”