COMMENTARY on 17:108
A. Yusuf Ali:

Translation:
"And they say: ´Glory to our Lord! Truly has the promise of our Lord been fulfilled!´" 2319
Commentary:

2319  Those who had received previous revelations find in the Qur'an and in the Messenger who brought it, the promise of Allah fulfilled. Those who were spiritually prepared for it found in the same way the satisfaction of their spiritual yearnings: to them, also, Allah's promise was sent to be fulfilled.

 

Muhammad Asad:

Translation:
and say, "Limitless in His glory is our Sustainer! Verily, our Sustainer's promise has been fulfilled!" 131
Commentary:
131  This may be an allusion to the many Biblical predictions of the advent of the Prophet Muhammad, especially to Deuteronomy xviii, 15 and 18 (cf. surah 2, note 33). In its wider sense, however, the "fulfilment of God's promise" relates to His bestowal of a definitive revelation, the Qur'an, henceforth destined to guide man at all stages of his spiritual, cultural and social development.