“Psalm 115:12 The Lord has been mindful of us; He will bless us; He will bless the house of Israel; He will bless the house of Aaron”

You would think that the house of Aaron, being the lineage of the priesthood, would be quite able to count themselves amongst the house of Israel and therefor count themselves amongst the blessed. But it’s never that straightforward. Reading in Exodus 28 we see that Aaron and his sons get given fine garments befitting the high priest, and it adds that Aarons will have a gold bells around the hem “and it’s tinkling shall be heard when he enters and leaves the place before the Lord, so that he will not die” v35
In chapter 29 you get the small matter of the sacrifices. What sacrifices the house of Aaron had made from the time of the consecration of the tabernacle to the time David penned his psalm? As the people kept sinning and returning the sacrifices would have kept being made, and the house of Aaron, I don’t doubt, would have occasionally looked on at the house of Israel and thought “how many more sacrifices must I do? How much more can they possibly sin? When is my rest?”. It was then, as I would put it, A Tough Gig.
What of today? Our house of Aaron I would argue is any Christian who sets themselves before Jesus and truly says “I am a servant to the Lord”. The sacrifices they make to the sinners in the House of Jesus seem as unending as those of the ancient priesthood, and as involved, bloody, smelly and wearisome as any animal sacrifice. But to those David singles out and sings over them a special blessing.