Psalms 115:10

O house of Aaron, trust in the Lord,.... The family of the tribe of Levi, that was separated from the rest, to minister in the priest's office, to offer gifts and sacrifices for the people, and to bless them; and therefore ought to trust in the Lord, and set a good example to others: as ministers of the word should, who are intrusted with much by the Lord, and should trust in him for much; for every supply of gifts and grace; and the rather, as they are to be examples of faith to the people: and as all the saints under the Gospel dispensation are priests unto God, they should put their trust and confidence in the Lord; since their sacrifices cannot be acceptable and wellpleasing to God, without faith in him.

He is their help and their shield; the Lord is the help and shield of everyone of Aaron's family; of the priests under the law, and of ministers under the Gospel; and of all those who are kings and priests unto God; and therefore they should trust in him. This is repeated for the certainty of it, and for the particular application of it to Aaron's house.