The joy of the vision of the risen Lord, the joy of the vision of glory
After having applied the comparison (of the woman in labor) to the sadness of the Apostles, the Lord applies it to their future joy.
First of all he promises them they will see him again when he says: “But I will see you again.” He does not say “you will see me” but “I will see you” because the fact of himself showing himself derives from his mercy, as shown by his look. And so he says: “But I will see you again” at the Resurrection and, in future glory: “Your eyes will see the king in his beauty” (Is 33:17).
He then promises them gladness of heart and rejoicing, saying: “and your hearts will be full of joy,” namely the joy of seeing me at the Resurrection. Therefore the Church sings: “This is the day the Lord has made, let us rejoice in it and be glad” (Ps 117[118]:24). “And your hearts will be full of joy” also because of the vision of glory: “You will fill me with joy in your presence” (Ps 15[16]:11). Indeed, it is natural for every living being to find their joy in contemplation of the beloved reality. Now, no one can see the divine essence without loving it. Therefore joy necessarily accompanies this vision: you will “see it” when you know it with the mind, “and your hearts will rejoice” (Is 60:5) and this joy will itself rise up again even as far as the body when it is glorified. And so Isaiah adds: “and your bones will flourish” (Is 66:14). “Enter into the joy of your Lord” (Mt 25:21).
Finally, the Lord promises a joy that will last forever when he says: “and your joy”, that which you will have at the Resurrection because of me – “I will greatly rejoice in the Lord” (Is 61:10) – “no one will take away from you” because “rising from the dead. Christ dies no more; death no longer has power over him” (Rm 6:9). Or again: “your joy” the joy of enjoying glory, “no one will take away from you” because it cannot be lost, it is everlasting: “everlasting joy will be on their heads” (Is 35:10).
In fact no one takes this joy away himself through sin because, in this instance, each one’s will has been confirmed in virtue; and no one, either, will take this joy away from another because in that place there will be no violence and none will bear a grudge against another.