Tafsir of Al-Mu'minoon 23:1-2

[The Linguistic Particle Qad] The particle qad here is the opposite of lamma. Qad affirms what is expected, whereas lamma negates it. There is no doubt that the believers were expecting such glad tidings—namely, the report confirming their success (falah). Thus, they were addressed with that which indicates the confirmation of what they expected.

[The Meaning of Falah] Falah means attaining one’s objective. It is also said to mean remaining in goodness. The verb aflaha (to succeed) means to enter into falah, just as abshara (to receive good news) means to enter into bishara. It is said: aflahahu (he caused him to succeed), meaning he brought him to falah. Based on this, there is the reading of Talha ibn Musarrif: ufliha (passive voice). Another reading from him is aflahu (they succeeded), following the grammatical structure of akaluni al-baraghith (the fleas ate me), or it may be interpreted as an ambiguous subject followed by an explanation. Another reading from him is aflu with a damma (vowel) without the waw, using the damma as a substitute for it, as in the poet’s saying: "If the physicians were around me..."

[Defining the Believer] If you ask: "What is a believer (mu'min)?" I say: In language, it is one who affirms the truth. In Islamic Law, there is a difference of opinion:

1. Every person who utters the two testimonies of faith, with their heart in agreement with their tongue, is a believer.
2. It is a descriptor of praise that only the righteous and pious deserve, not the corrupt and wretched.

[The Meaning of Khushu' (Humility/Reverence)] It is the fear of the heart and the lowering of the gaze. Qatada said: "It is fixing the gaze upon the place of prostration." It is narrated that the Prophet (ﷺ) used to pray while looking toward the sky, but when this verse was revealed, he cast his gaze toward his place of prostration. When a scholar stood for prayer, he would fear the Most Merciful too much to fix his gaze on anything or occupy his mind with worldly affairs.

It is also said: It is the gathering of one’s focus for prayer and turning away from everything else. Part of khushu' is observing proper etiquette: avoiding tucking up one’s garment, fidgeting with one’s body or clothes, looking around, stretching, yawning, closing the eyes, covering the mouth, letting the garment hang (sadl), cracking knuckles, interlocking fingers, placing hands on the hips, or flipping pebbles.

It is narrated that the Prophet (ﷺ) saw a man fidgeting with his beard during prayer and said: "If his heart were humble, his limbs would be humble." Al-Hasan saw a man playing with pebbles while saying, "O Allah, marry me to the maidens of Paradise," and said: "What a poor suitor you are! You propose while you are fidgeting."

[Why is Prayer Attributed to Them?] If you ask: "Why is the prayer attributed to them (i.e., 'their prayer')?" I say: Because prayer revolves between the one praying and the One to whom it is prayed. The one praying is the sole beneficiary of it; it is his provision and his treasure, hence it is "his prayer." As for the One to whom it is prayed, He is Rich and Exalted above any need for it or benefit from it.