Commentaries:
Barnes' Notes
Believe me - As she had professed to believe that he was a prophet, it was right to require her to put faith in what he was about to utter. It also shows the importance of what he was about to say.
The hour cometh - The time is coming, or is near.
When neither in this mountain ... - Hitherto the public solemn worship of God has been confined to one place. It has been a matter of dispute whether that place should be Jerusalem or Mount Gerizim. That controversy is to be of much less importance than you have supposed. The old dispensation is about to pass away. The special rites of the Jews are to cease. The worship of God, so long confined to a single place, is soon to be celebrated everywhere, and with as much acceptance in one place as in another. He does not say that there would be no worship of God in that place or in Jerusalem, but that the worship of God would not be "confined" there. He would be worshipped in other places as well as there.
Other Barnes' Notes entries containing John 4:21:
Malachi 1:11
Matthew 10:5
John 2:4
Acts 21:5
1 Timothy 2:8
1 Peter 2:5
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