Tafsir of An-Naba' 78:14

And We have sent down from the Mu`sirat water Thajjaj. Ali bin Abi Talhah reported from Ibn Abbas that he said, "From the Mu`sirat means from the clouds.'' This was also stated by Ikrimah, Abu Al-`Aliyah, Ad-Dahhak, Al-Hasan, Ar-Rabi` bin Anas, Ath-Thawri, and it is preferred by Ibn Jarir. Al-Farra' said, "They are the clouds that are filled with rain, but they do not bring rain. This is like the woman being called Mu`sir when (the time of) her menstrual cycle approaches, yet she does not menstruate.'' This is as Allah says,

الله الذى يرسل الريح فتثير سحابا فيبسطه فى السماء كيف يشاء ويجعله كسفا فترى الودق يخرج من خﻼله

Allah is He Who sends the winds, so that they raise clouds, and spread them along the sky as He wills, and then break them into fragments, until you see rain drops come forth from their midst! meaning, from its midst. (30:48) Concerning Allah's statement,

ماء ثجاجا

(water Thajjaj) Mujahid, Qatadah, and Ar-Rabi` bin Anas all said, "Thajjaj means poured out.'' At-Thawri said, "Continuous.'' Ibn Zayd said, "Abundant.'' In the Hadith of the woman with prolonged menstrual bleeding, when the Messenger of Allah said to her,

أنعت لك الكرسف

I suggest you to make an absorbent cloth for yourself.'' Meaning, `dress the area with cotton.' The woman replied, "O Messenger of Allah! It (the bleeding) is too much for that. Verily, it flows in profusely (Thajja).'' This contains an evidence for using the word Thajj to mean abundant, continuous and flowing. And Allah knows best. Allah said,

لنخرج به حبا ونباتا