Psalms 115:9

“O Israel, trust thou in the Lord, etc.] Or, “the house of Israel hath trusted in the Lord”: so the Septuagint, Vulgate Latin, Syriac, Arabic, and Ethiopic versions: the Targum is, “Israel trusteth in the Word of the Lord;” in distinction from the Heathens, that trust in their idols. But it is better rendered as an imperative, trust thou; it being an exhortation to Israel to trust in the Lord, in opposition to idols; and may be understood of Israel, literally taken, who were God’s chosen covenant people, to whom he had made a revelation of himself, and of his will; and therefore should trust in him, and in no other; and of spiritual Israel, or all the elect of God, and redeemed of the Lamb;…”

“O Israel, trust thou in the Lord - This exhortation is founded in a great measure on what had been just said in regard to idols. They had no power. There was no reason why they should be confided in. They could not help in the day of trouble; and as people need a god, and as the idols cannot be to them as gods, the exhortation is addressed to his people to trust him. He would be to them all that was implied in the name God; all that was wanted in a God. He is their help - The help of those who trust in him. He is able to help them in the time of trouble; he is willing to help them; he will help them. They who put their trust in him will find him a sure and certain help. This is the…”

“Their - Who trust in him. Psalms 115:10”

“115:9-11 Israel . . . priests . . . you who fear the Lord: The psalmist calls on all those in the God-fearing community to commit their ways to the living God. The threefold address assures them that the Lord is their true helper and shield (cp. 118:2-4).”

“Israel: Psa 118:2-4, Psa 135:19, Psa 135:20; Exo 19:5 trust: Psa 62:8, Psa 125:1, Psa 130:7, Psa 146:5, Psa 146:6; Jer 17:17, Jer 17:18; Eph 1:12 their help: Psa 33:20, Psa 33:21, Psa 84:11; Deu 33:29; Pro 30:5 Psalms 115:10”

“After this confession of Israel there now arises a voice that addresses itself to Israel. The threefold division into Israel, the house of Aaron, and those who fear Jahve is the same as in Psa 118:2-4. In Ps 135 the "house of Levi" is further added to the house of Aaron. Those who fear Jahve, who also stand in the last passage, are probably the proselytes (in the Acts of the Apostles σεβόμενοι τὸν Θεόν, or merely σεβόμενοι) (Note: The appellation φοβούμενοι does not however occur, if we do not bring Act 10:2 in here; but in Latin inscriptions in Orelli-Hentzen No. 2523, and in Auer in the Zeitschrift fr katholische Theologie 1852, S. 80, the proselyte (religionis Judaicae) is called…”