Tafsir of At-Tariq 86:12

"And the Earth with its cleft" refers to what the Earth splits open with, namely vegetation. Its root meaning is the "split" (al-shaqq), and vegetation has been named with this term metaphorically. Or, it may be an infinitive (masdar) derived from a passive construction, in which case the intended meaning is its being split by vegetation; this has been narrated from Atiyyah and Ibn Zayd.

It has been said that it refers to its splitting by springs, but this is refuted by the fact that the description of the heaven and the earth when swearing by them is to attest to the truth of the Quran—which speaks of the Resurrection—through the two mentioned descriptions. This serves to gesture toward the fact that they, in themselves, are among its witnesses. This is the secret behind expressing rain as "al-raj'" (the return), for that corresponds to the splitting of the earth with vegetation, which mimics the Resurrection as mentioned in several places in the Revelation, unlike its splitting by springs. From this, one understands the weakness in interpreting "al-raj'" as something other than rain, and likewise, the weakness in the statement of Mujahid that "al-sad'" (the cleft) refers to the fissures, valleys, and trenches on earth, or its splitting by the sea and other things. Also considered weak is what was narrated from him that "al-sad'" means the paths that pedestrians carve out. It has also been said that it means "possessor of the dead," because it splits open to release them for the Resurrection.