COMMENTARY on 57:12
A. Yusuf Ali:

Translation:
One Day shalt you seest the believing men and the believing women- how their Light runs 5288 forward before them and by their right hands: (their greeting will be): "Good News for you this Day! Gardens beneath which flow rivers! to dwell therein for aye! This is indeed the highest Achievement!" 5289
Commentary:

5288  In the Darkness of the Day of Judgement there will be a Light to guide the righteous to their Destination. This will be the Light of their Faith and their Good Works. Perhaps the Light of the Right Hand mentioned here is the Light of their Good Works: for the Blessed will receive their Record in their right hand (69:19- 24).

5289  The highest Achievement, the highest felicity, the attainment of Salvation, the fulfillment of all desires. See n. 4733 to 44:57.

 

Muhammad Asad:

Translation:
on the Day when thou shalt see all believing men and believing women, with their light spreading rapidly before them and on their right, 12 [and with this wel­come awaiting them:] “A glad tiding for you today: gardens through which running waters flow, therein to abide! This, this is the triumph supreme!”
Commentary:
12  See note 25 on the expression ashab al-yamin ("those on the right hand") in 74:39. In many instances, the metaphor of "the right hand" or "right side" is used in the Qur’an to denote "righteousness" and, therefore, "blessedness", symbolized in the present context by the "light spreading rapidly" before and on the right side of the believers as a result of their "cognition of God, and their high morality, and their freedom from ignorance and blameworthy traits" (Razi).