v. 36 — While ye have the Light, believe on the Light, that ye may become sons of Light.
Commentary on the Gospel according to John · St Cyril of Alexandria
He proved therefore that the faith which is in Him, through Whom a man comes to the knowledge also of the Father, is the way of salvation. And He names them sons of Light whether of Himself or of the Father, for He speaks of the Father as Light after having spoken of Himself as Light----in order to show that the Nature of Himself and of His Father is One: and we become sons of the Father, when, through the faith which is in Christ, we accept the Father Who is Light; for then shall we also be entitled children of God.
CyrJn 8.36.1
After teaching them in few words what was profitable, once again by God-befitting power He betakes Himself from their midst, concealing Himself; and not permitting them to be roused to anger, but giving them opportunity to change their mind, with intent that they might do what was better. And He withdraws with a set purpose, His Passion being nigh; shewing that it was not His will to be put to death by the Jews, notwithstanding that He willingly yielded Himself up to suffer, giving Himself a Ransom for our life; and accepted death, which men naturally liken unto sorrow, and changed the sorrow into gladness.
CyrJn 8.36.3