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 13
On title, see Introduction. The Psalmist, mourning God's absence and the triumph of his enemies, prays for relief before he is totally destroyed, and is encouraged to hope his trust will not be in vain. (Psa 13:1-6)
The forms of expression and figure here used are frequent (compare Psa 9:12, Psa 9:18; Psa 10:11-12).
How long . . . for ever--Shall it be for ever?
The counsels or devices of his heart afford no relief.
lighten mine eyes--dim with weakness, denoting approaching death (compare Sa1 14:27-29; Psa 6:7; Psa 38:10).
rejoice--literally, "shout as in triumph."
I am moved--cast down from a firm position (Psa 10:6).
Trust is followed by rejoicing in the deliverance which God effects, and, instead of his enemy, he can lift the song of triumph.