Jamieson, Fausset and Brown on Psalms 50:8-15

8-15. However scrupulous in external worship, it was offered as if they conferred an obligation in giving God His own, and with a degrading view of Him as needing it [Psa 50:9-13]. Reproving them for such foolish and blasphemous notions, He teaches them to offer, or literally, "sacrifice," thanksgiving, and pay, or perform, their vows--that is, to bring, with the external symbolical service, the homage of the heart, and faith, penitence, and love. To this is added an invitation to seek, and a promise to afford, all needed help in trouble.