Charles H. Spurgeon on Psalms 115:9

He is their help. We should rather have expected, "Our help and our shield, "&c. But the burden thrice introduced, appears to be a well known formula of praise. "Their, "i.e., "of all who trust in him." The verses contain a climax: (1) Israel in general is addressed; (2) the priests or ministers of God's service; (3) the true Israelites; not only chosen out of all people, or out of the chosen people for outward service; but serving God in sincerity of heart. Speaker's Commentary.