While the sun, or the light, or the moon, or the stars, are not darkened, nor the {a} clouds return after the rain:

(a) Before you come to a continual misery: for when the clouds remain after the rain, man's grief is increased.

Wesley's Notes

12:2 Which - Heb. While the sun, and the light, and the moon, and c. That clause, and the light, seems to be added to signify that he speaks of the darkening of the sun, and moon, and stars; not in themselves, but only in respect of that light which they afford to men. And therefore the same clause which is expressed after the sun, is to be understood after the moon and stars. And those expressions may be understood of the outward parts of the body, and especially of the face, the beauty of the countenance, the pleasant complexion of the cheeks, the liveliness of the eyes, which are compared to the sun, and moon, and stars, and which are obscured in old age, as the Chaldee paraphrast understands it. Or of external things, of the change of their joy, which they had in their youth, into sorrow, and manifold calamities, which are usually the companions of old age. This interpretation agrees both with the foregoing verse , in which he describes the miseries of old age, and with the following clause, which is added to explain those otherwise ambiguous expressions; and with the scripture use of this phrase; for a state of comfort and happiness is often described by the light of the sun, and a state of trouble is set forth, by the darkening of the light of the sun. Nor the clouds - This phrase denotes a perpetual succession of rain, and clouds bringing rain, and then rain and clouds again. Whereby he expresses either the rheums or destructions which incessantly flow in old men; or the continual vicissitude of infirmities, diseases, and griefs; one deep calling upon another.

Jamieson-Fausset-Brown Bible Commentary

2. Illustrating "the evil days" (Jer 13:16). "Light," "sun," &c., express prosperity; "darkness," pain and calamity (Isa 13:10; 30:26).

clouds . after . rain-After rain sunshine (comfort) might be looked for, but only a brief glimpse of it is given, and the gloomy clouds (pains) return.

Matthew Henry's Concise Commentary

12:1-7 We should remember our sins against our Creator, repent, and seek forgiveness. We should remember our duties, and set about them, looking to him for grace and strength. This should be done early, while the body is strong, and the spirits active. When a man has the pain of reviewing a misspent life, his not having given up sin and worldly vanities till he is forced to say, I have no pleasure in them, renders his sincerity very questionable. Then follows a figurative description of old age and its infirmities, which has some difficulties; but the meaning is plain, to show how uncomfortable, generally, the days of old age are. As the four verses, 2-5, are a figurative description of the infirmities that usually accompany old age, ver. 6 notices the circumstances which take place in the hour of death. If sin had not entered into the world, these infirmities would not have been known. Surely then the aged should reflect on the evil of sin.