From a sermon by Martin Luther on the Nativity of the Christ:
Many in this congregation think to themselves, "If only I had been there! How quick I would have been to help the Baby! I would have washed His linen. How happy I would have been to go with the shepherds to see the Lord lying in the manger!
Yes, you would! You say that because you know how great Christ is, but if you had been there at that time you would have done no better than the people of Bethlehem. Childish and silly thoughts are these!
Why don't you do it now? You have Christ in your neighbor. You ought to serve him, for what you do to your neighbor in need you do to the Lord Christ Himself.
Taken from "Hear I Stand," page 354