Tafsir of An-Najm 53:9

(So it was) — meaning Jibril (peace be upon him) in relation to the Prophet (may Allah exalt his mention and grant him peace) — (a distance of two bows). This refers to the bows of the Arabs, as an unrestricted term defaults to what is customary among them. Al-Qab (the span/measure), as well as al-qib, al-qad, al-qid, al-qais, and al-miqdar (the measure), all carry the same meaning. Zayd ibn Ali recited it as qad, and it has been recited as qid, qadr, and qudr. Measurements are commonly expressed by bows, just as they are by spears, cubits, and others. It is said that the qab is the distance between the grip of the bow and its siyah (the curved end); thus, every bow has two qabs, and it is interpreted as such here. It has been said that there is a transposition (qalb) in the phrasing, meaning qabai qawsain (the two spans of two bows). In al-Kashf, it is noted that you may say qaban qaws or qaba qawsain without transposition. According to Mujahid and al-Hasan, the qab of a bow is the distance between its string and its grip; there is no need for transposition based on this either. This — as al-Khafaji stated — is a reference to what the Arabs used to do in the Pre-Islamic era when they formed an alliance: they would take two bows and bind them together so that their qabs were adjacent, appearing as if they were a single span. Then, they would draw them together and shoot a single arrow from them. This served as an indication that the pleasure of one was the pleasure of the other, and the wrath of one was the wrath of the other, such that opposition was impossible.

It is reported from Ibn Abbas that the "bow" here is a cubit used for measuring lengths; Abu Razin held this view, and al-Tha'labi mentioned that this is from the dialect of the Hijaz. In any case, the meaning rests upon the omission of a genitive possessor (mudaf), meaning "he was possessing the distance of two bows." Similar is the saying: "And the 'arad (wild she-camel) reached its limping, and you have made me like a finger of Khuzaima," which implies the size/measure of a finger. It denotes proximity; as if it were said: "He was close to him." It is also permissible that the pronoun in kana refers to the distance, interpreting it as "the space" or similar, and thus there is no need to assume an omission; though this view is not strong.

(Or closer) — meaning, or nearer than that. The "or" (aw) implies doubt from the perspective of the observer, meaning that when the observer sees him, he says: "He is a distance of two bows or closer." The intent is to convey the intensity of the proximity.