A.T. Robertson Commentary John 3:17

"For God sent not the Son into the world to judge the world; but that the world should be saved through him." — John 3:17 (ASV)

For God sent not the Son (ου γαρ απεστειλεν ο θεος τον υιον). Explanation (γαρ) of God's sending the Son into the world. First aorist active indicative of αποστελλω. John uses both αποστελλω from which comes αποστολος (3:34; 5:36,38, etc.) and πεμπω (4:34; 5:23,24,30, etc.) for God's sending the Son and πεμπω more frequently, but with no real difference in meaning. All the Gospels use ο υιος in the absolute sense in contrast with the Father (Matthew 11:27; Luke 10:22).

To judge (ινα κρινη). Final clause with ινα and the present (or aorist) active subjunctive of κρινω. The Messiah does judge the world as Jesus taught (Matthew 25:31f.; John 5:27), but this was not the primary or the only purpose of his coming. See on Mt 7:1 for κρινω, to pick out, select, approve, condemn, used so often and in so many varying contexts in the N.T.

But that the world should be saved through him (αλλ ινα σωθη ο κοσμος δι' αυτου). First aorist passive subjunctive of σωζω, the common verb to save (from σως, safe and sound), from which σωτηρ (Saviour) comes (the Saviour of the world, 4:42; 1 John 4:14) and σωτηρια (salvation, 4:22 here only in John). The verb σωζω is often used for physical health , but here of the spiritual salvation as in 5:34.