The joy of salvation
The turning of their grief to joy (20) is illustrated by Jesus with a comparison with child birth (21). Just as the joy of a new-born child far outweighs the memory of the pain that precedes it, so the grief of Jesus’s death will quickly give way to the joy of his resurrection. Moreover the pain of childbirth is itself a sign and promise of something wonderful about to happen.
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God’s salvation was about to be birthed. In contrast to the failed mission of Israel (“We gave birth to wind. We have not brought salvation to the world.” Isaiah 26:17-19), Jesus by his death and resurrection would save his people from their sins (Matt.1:21; 1 Pet.2:24; Rom.1:4). So the resurrection appearances of Jesus to the disciples were the basis of a joy that was not simply the end of grief but the joy of salvation (22; Isaiah 12:3).
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No one can take away this kind of joy, because it is not dependent on Jesus’s physical presence or on any circumstances. Through the resurrection of Jesus Christ, we can rejoice despite our trials: “Even though you do not see him now, you believe in him and are filled with an inexpressible and glorious joy, for you are receiving the salvation of your souls” (1 Pet.1:3-9).