But after I am risen - This promise was given them to encourage and support them, and also to give them an indication where he might be found.
He did not deny that he would first appear to a part of them before he met them all together (compare Luke 24:13-31, Luke 24:34; 1-Corinthians 15:5), but that he would meet them all in Galilee. This was done. See Mark 16:7; Matthew 28:16.
Galilee - See the notes at Matthew 2:22.

But after I am risen again - Don't lose your confidence; for though I shall appear for a time to be wholly left to wicked men, and be brought under the power of death, yet I will rise again, and triumph over all your enemies and mine.
I will go before you - Still alluding to the case of the shepherd and his sheep. Though the shepherd has been smitten and the sheep scattered, the shepherd shall revive again, collect the scattered flock, and go before them, and lead them to peace, security, and happiness.

But after I am risen again,.... This he says for their comfort, that though he, their shepherd, should be apprehended, condemned, and crucified, should be smitten with death, and be laid in the grave, yet he should rise again; and though they should be scattered abroad, yet should be gathered together again by him, their good shepherd; who would after his resurrection, appear to them, be at the head of them, and go before them, as a shepherd goes before his sheep: for it follows,
I will go before you into Galilee; the native place of most, if not all of them. This the women that came to the sepulchre after Christ's resurrection, were bid, both by the angel, and Christ himself, to remind the disciples of, and ordered them to go into Galilee, where they might expect to see him: accordingly they did go thither, and saw and worshipped him; see Matthew 28:7.

I will go before you into Galilee. The first announcement of the great Galilean meeting of the risen Lord with his disciples. See Matthew 28:16; John 21; 1-Corinthians 15:6.

But notwithstanding this, after I am risen I will go before you (as a shepherd before his sheep) into Galilee. Though you forsake me, I will not for this forsake you.