The Right To Become A Child Of God

In John 1:12, the apostle writes that 'to all who received him, who believed in his name, he gave the right to become children of God.' On August 25, 1537, Martin Luther entered a pulpit in Denmark to fill in for a friend and preached on this text.

No man, no matter, who he may be, can ponder the magnificence sufficiently or express it adequately in words. We poor mortals, who are condemned and miserable sinners through our first birth from Adam, are singled out for such great honor and nobility that the eternal and almighty God is our Father and we are His children. Christ is our Brother, and we are His fellow heirs (Rom 8:17). And the dear angels, such as Michael and Gabriel, are not to be our masters but our brothers and servants. . . .
This is a grand and overpowering thought! Whoever really reflects on it--the children of the world will not, but Christians will, although not all of them either--will be so startled and frightened by the thought that he will be prompted to ask: 'My dear, can this really be possible and true?'
. . . [T]he world rates it a much higher honor and privilege to be the son and heir of a prince, a king, or a count than to be the possessor of God's spiritual goods, although by comparison all these are nothing but poor bags of worms and their glory sheer stench. Just compare all this with the ineffable dignity and nobility of which the evangelist speaks. . . . If we really believed with all our heart, firmly and unflinchingly, that the eternal God, Creator and Ruler of the world, is our Father, with whom we have an everlasting abode as children and heirs, not of this transitory wicked world but of all God's imperishable, heavenly, and inexpressible treasures, then we would, indeed, concern ourselves but little with all that the world prizes so highly; much less would we covet it and strive after it.

Indeed, we would regard the world's riches, treasures, glories, splendor, and might--compared with the dignity and honor due us as the children and heirs, not of a mortal emperor but of the eternal and almighty God--as trifling, paltry, vile, leprous, yes, as stinking filth and poison.
--Luther, preaching on John 1:12, in LW 22:87-89