A Commentary, Critical, Practical, and Explanatory on the Old and New Testaments, by Robert Jamieson, A.R. Fausset and David Brown [1882] at sacred-texts.com
Psalms Chapter 138
David thanks God for His benefits, and anticipating a wider extension of God's glory by His means, assures himself of His continued presence and faithfulness. (Psa 138:1-8)
I will praise thee with my whole heart--(Compare Psa 9:1).
before the gods--whether angels (Psa 8:5); or princes (Exo 21:6; Psa 82:6); or idols (Psa 97:7); denotes a readiness to worship the true God alone, and a contempt of all other objects of worship.
(Compare Psa 5:7).
thy word above all thy name--that is, God's promise (Sa2 7:12-16), sustained by His mercy and truth, exceeded all other manifestations of Himself as subject of praise.
That promise, as an answer to his prayers in distress, revived and strengthened his faith; and, as the basis of other revelations of the Messiah, it will be the occasion of praise by all who hear and receive it (Psa 68:29, Psa 68:31; Isa 4:3).
for great is the glory--or, "when the glory shall be great," in God's fulfilling His purposes of redemption.
On this general principle of God's government (Isa 2:11; Isa 57:15; Isa 66:2), he relies for God's favor in saving him, and overthrowing his enemies.
knoweth afar off--their ways and deserts (Psa 1:6).
God will fulfil His promise.