"And O my people, seek forgiveness of your Lord"
(i.e., from polytheism), "then repent to Him" (i.e., return to Him, Exalted be He, through obedience, or repent to Him, Glorified be He, by making the repentance sincere and remaining steadfast upon it). It is said: Seeking forgiveness is a metonymy for faith because it is among its synonyms. Since faith in Allah, Glorified be He, does not linguistically necessitate disbelief in others, it was said: "then repent to Him," as if it were said: Believe in Him, then repent to Him, Exalted be He, from the worship of others. This is countered by the fact that His statement, "Worship Allah," indicated His—Exalted be He—exclusivity in worship; therefore, if "seek forgiveness" were interpreted as mentioned, it would yield no additional benefit beyond what was already attached to it, and it would have been possible to attach it to the first. Interpreting it in a way other than the apparent meaning, while possessing little benefit, is something that must be avoided regarding the miraculous speech of Allah, Exalted be He.
It is also said that the intended meaning of seeking forgiveness is repentance from polytheism, and repentance is repentance from what was committed by them other than polytheism. It is countered by the fact that faith wipes away what came before it. It is also said that the intended meaning of the first is seeking forgiveness through faith, and the second is seeking to draw near to Him, Glorified be He, through repentance from polytheism. It is countered by the fact that the mentioned drawing near is inseparable from seeking forgiveness through faith, as it is one of its concomitants, and thus it would not be "after" it, as "then" (thumma) implies. Other interpretations have been mentioned, and some discussion on this has preceded at the beginning of the Surah.
"And He will send the sky upon you" (i.e., the rain, as in the saying: "When the sky descends upon a land of a people, we graze it even if they are angry"). "In torrents" (i.e., abundant in flow, continuous without harm; it is in the pattern of mif'al for exaggeration, like mi'tar and miqdam).
"And add strength to your strength" (i.e., might added to your might, or with your might). This returns to His statement, Exalted be He, "And provide you with wealth and children," because worldly might consists of that. From al-Dahhak, there is an interpretation of strength as fertility; from 'Ikrimah, an interpretation of it as grandchildren. It is said: The intended meaning is bodily strength. He—peace be upon him—tempted them with abundant rain and an increase in strength because they were people of crops, gardens, and buildings. It is said: Allah, Exalted be He, withheld rain from them and rendered the wombs of their women barren for three years, so Hud—peace be upon him—promised them, upon their seeking forgiveness and repentance, abundant rains and a doubling of strength through procreation. It is said: The first strength is in faith and the second is in the bodies, meaning: He will add strength in your faith to the strength of your bodies.
"And do not turn away" (i.e., do not turn away from what I have called you to), "as criminals" (i.e., persisting in the crime you are upon). It is said: "Criminals" by turning away, though this is forced.