Charles Ellicott Commentary John 16:21

"A woman when she is in travail hath sorrow, because her hour is come: but when she is delivered of the child, she remembereth no more the anguish, for the joy that a man is born into the world." — John 16:21 (ASV)

A woman when she is in travail hath sorrow.—The Greek is more exactly, the woman . . . has pangs—that is, “the woman in the well-known illustration.” (See Note on John 15:15.) This figure was of frequent use in the prophets. (Isaiah 26:17–18, and especially Isaiah 66:7-8; Jeremiah 4:31; Jeremiah 22:23; Jeremiah 30:6; Hosea 13:13–14; Micah 4:9–10.)

That a man is born into the world.—The word is the wider word for “human being.” (Compare to Note on John 1:51.) The thought is of the joy of maternity swallowing up the pangs of childbirth. These cease to exist, but that continues. She forgets the one in the fullness of the other.

For the phrase “into the world” compare to John 1:9; John 18:37.