Tafsir of Al-Muzzammil 73:6

{ناشئة الليل}: The soul that arises at night, which rises from its bed for worship. That is: it stands up and ascends. It is derived from the phrase "the cloud arose" (nash'at al-sahaba), meaning it ascended. Similarly, "he arose from his place" (nasha'a min makanihi) and "he stood up" (nashaza) mean he rose. A poet said: We arose toward the camels, whose fat was worn away by night travel, And whose high-reaching humps were made lean.

It also refers to the act of standing at night (qiyam al-layl), on the basis that nashi'a is a verbal noun (masdar) from nasha'a (to stand or rise), following the pattern of fa'ila (like al-'aqiba). This is supported by what is narrated from 'Ubayd ibn 'Umayr: "I said to 'A'isha, 'If a man stands at the beginning of the night, do you say he has performed a nashi'a?' She replied, 'No; the nashi'a is the standing after sleep.'"

Thus, she interpreted nashi'a as the act of rising from one's bed, or the worship that arises at night—meaning it occurs and ascends. It is also said: it refers to all the hours of the night, because they occur one after another. Others say: it refers to the first hours of the night.

'Ali ibn al-Husayn (may Allah be pleased with them both) used to pray between Maghrib and 'Isha and say, "Have you not heard the saying of Allah Almighty: {إن ناشئة اليل}? This is the nashi'a of the night."

{هي أشد وطأ}: It is specifically—unlike the nashi'a of the day—more conducive to the heart agreeing with the tongue (if you mean the soul). Or, it causes the heart of the one standing to agree with his tongue (if you mean the standing, the worship, or the hours). Or, it is more in agreement with the desired state of humility and sincerity.

Al-Hasan said: It is more in agreement between the secret and the public, due to the absence of the sight of created beings.

It is recited as ashaddu wat'an (with a fatha) and wit'an (with a kasra). The meaning is: firmer in footing and further from slipping. Or, it is heavier and more burdensome upon the worshiper than the prayer of the day, derived from the Prophet's (peace be upon him) saying: (O Allah, intensify Your grip [wat'ataka] upon Mudar).

{وأقوم قيلا}: More correct in speech, and more established in recitation due to the stillness of voices.

Anas (may Allah be pleased with him) once recited: wa-aswabu qila (more accurate in speech). It was said to him, "O Abu Hamza, it is actually wa-aqwamu (more upright)." He replied, "Aqwamu, aswabu, and ahya' (more prepared) are all one [in meaning]."

Abu Zayd al-Ansari narrated from Abu Sarar al-Ghanawi that he used to recite: fa-hasu (with an unpointed ha). It was said to him, "It is actually jasu (with a jim)." He replied, "Jasu and hasu are one."