For he whom God hath sent speaketh the words of God: for God giveth not the Spirit by measure unto him.

Wesley's Notes

3:34 God giveth not him the Spirit by measure - As he did to the prophets, but immeasurably. Hence he speaketh the words of God in the most perfect manner.

Jamieson-Fausset-Brown Bible Commentary

34. for God giveth not the Spirit by measure-Here, again, the sharpest conceivable line of distinction is drawn between Christ and all human-inspired teachers: "They have the Spirit in a limited degree; but God giveth not [to Him] the Spirit by measure." It means the entire fulness of divine life and divine power. The present tense "giveth," very aptly points out the permanent communication of the Spirit by the Father to the Son, so that a constant flow and reflow of living power is to be understood (Compare Joh 1:15) [Olshausen].

Matthew Henry's Concise Commentary

3:22-36 John was fully satisfied with the place and work assigned him; but Jesus came on a more important work. He also knew that Jesus would increase in honour and influence, for of his government and peace there would be no end, while he himself would be less followed. John knew that Jesus came from heaven as the Son of God, while he was a sinful, mortal man, who could only speak about the more plain subjects of religion. The words of Jesus were the words of God; he had the Spirit, not by measure, as the prophets, but in all fulness. Everlasting life could only be had by faith in Him, and might be thus obtained; whereas all those, who believe not in the Son of God, cannot partake of salvation, but the wrath of God for ever rests upon them.