A.T. Robertson Commentary John 12:36

"While ye have the light, believe on the light, that ye may become sons of light. These things spake Jesus, and he departed and hid himself from them." — John 12:36 (ASV)

Believe in the light (πιστευετε εις το φως). That is, "believe in me as the Messiah" (8:12; 9:5).

That ye may become sons of light (ινα υιο φωτος γενησθε). Purpose clause with ινα and second aorist subject of γινομα, to become. They were not "sons of light," a Hebrew idiom (cf. 17:12; Luke 16:8 with the contrast), an idiom used by Paul in 1 Thessalonians 5:5; Ephesians 5:8. It is equivalent to "enlightened men" (Bernard) and Jesus called his disciples the light of the world (Matthew 5:14).

Hid himself from them (εκρυβη απ' αυτων). Second aorist passive indicative of κρυπτω, late form (in LXX) for old εκρυφη, "was hidden from them," as in 8:59. This part of verse 36 begins a new paragraph.