At Exodus 28:41 (in the Greek Septuagint), we read the following instructions of God when He was talking to Moses about the special garments that were to be worn by those that served as the Holy Priests of IsraEl:
‘You must put them [the garments] upon your brother Aaron and his sons, then anoint them and empower their hands. Make them Holy, so that they can officiate as Priests before Me.’
In Greek, the highlighted words are, kai empleseis auton tas cheiras, or, and fill of them the hands. So it’s possible that the verses are saying that Aaron and his sons were to undergo some sort of empowerment ceremony following their anointing.