Tafsir of Al-Isra 17:108

ويقولون سبحان ربنا

And they say: Glory be to our Lord!, meaning, they extol and glorify their Lord for His perfect power and for not delaying the fulfillment of the promise which He made through His earlier Prophets, that He would send Muhammad. Hence they said:

سبحان ربنا إن كان وعد ربنا لمفعوﻻ

Glory be to our Lord! Truly, the promise of our Lord must be fulfilled