Here’s a wonderful excerpt from a sermon Martin Luther preached on Isaiah 9:1-7 (Christmas Day, 1532).
“Thus, now, we hear how wonderfully and lovingly the prophet Isaiah describes Christ. He is a child and son, he says, who is born and given to us, is a Lord and possesses a government. But what kind of a Lord is he? He is a Lord who bears us and on whose shoulder we lie. If he does not bear us, we are lost. If pope, bishops, monks, and priests believed this, they would deal much differently with this matter. However, they do not want to be borne by Christ; instead they bear Christ, as they seem to think, and to them Christ is merely a painted Christ. For in their thinking they believe they are to live in this or that manner, fast and pray, do enough to pay for their sins and appease God’s anger.”
“But that sort of carrying is contradictory. If Christ does not bear you but you try to bear him, that will be a very heavy load for you, just as if a lost and strayed sheep would say to its shepherd who wanted to carry it: No, dear shepherd, you are not to carry me; I wish to carry you; sit on me! Obviously that sheep would be crushed by the load.”
“But if the sheep is to be helped, the sheep must speak like this: Accept my thanks, dear Shepherd, for seeking and carrying me; I cannot carry you, but I shall let you carry me.”
“So also in Christ’s kingdom! Christ wants to carry his sheep, just like a shepherd carries a poor, wretched, strayed sheep. He speaks to a poor sinner in this manner: You are conceived and born in sin, you have angered God by many sins and are condemned to death; but you are not to suffer anguish on account of this, for your sins are forgiven you; simply lie on my shoulder, I want to carry you before God.”
This sermon and quote is in Volume 7 (pages 227-8) of The Complete Sermons of Martin Luther.