John 21:15-19 is the Lord graciously letting Peter affirm 3 times that he loves Him, after having denied Him 3 times. By "feeding" the lambs and sheep, he will be what? yes, preaching the Gospel and the Word, to them. We show our love in the same way, by fulfilling the great commission.
Everyone is commissioned to do that, though. Jesus is specifically, personally commissioning Peter to do something that not everyone is personally commissioned to do.