Charles Ellicott Commentary John 16:30

"Now know we that thou knowest all things, and needest not that any man should ask thee: by this we believe that thou camest forth from God." — John 16:30 (ASV)

Now are we sure that you know all things.—Compare to John 16:19; John 16:23. The “now” is emphatic, as in the previous verse. They see in His present knowledge of their thoughts, and in the light that has come to them from the statements of John 16:28, the fulfillment of the promise He has made for the future (John 16:23). They think that the day has already come when they will ask Him nothing, because He knows all things and communicates to them the fullness of truth.

By this we believe that you came forth from God.—They had believed this before (John 16:27), but here, as frequently, St. John remembers the development of their faith. (Compare to the Note on John 2:11.) They find, in His knowledge of their thoughts (John 16:19), and in the full solution that He gives to their difficulties, ground for a new faith; and upon this new proof of His divinity they have a new faith in Him. (Compare to the instance of Nathanael’s faith at the end of John 1:0.)