“Here you learn what a great glory and what an ineffable eternal treasure the advent of God’s Son brought to those who accept Him, believe in Him, and regard Him as the Man sent by God to help the world.
They believe that He is to be the new means and agency for the bestowal of both the power and the prerogative of children of God upon all who believe in His name.
If we believe that He is the eternal Word of the Father through whom all things were made (John 1:3); if we believe that He is the Light and the Life of man (John 1:4) and the Lamb of God which bears the sins of the world (John 1:29) and removes these sins and casts them into the depths of the sea, as the prophet Micah said (Micah 7:19); if we call upon Him in every need and thank Him for His inexpressible grace and benefits—then we shall have the singular privilege, liberty, and right to be the dear children of a gracious Father in heaven, to be heirs of all His eternal and heavenly goods, to be, as Paul declares in Rom. 8:17, the brethren and fellow heirs of Christ, and to have salvation and life eternal.
How is this to be understood? Did He grant this power and privilege to all men, who, as we know, are all children of wrath (Eph. 2:3)?
The evangelist replies: ‘No, not to all; but to all without limit and to the exclusion of none who believe in His name; this means, to all who accept His Word in faith, who remain steadfast and call upon Him.’
Here you hear explicitly that this high honor, glorious liberty, and power to become the children of God can be attained through no other means or method than solely through a knowledge of, and faith in, Christ.
Ascetic life, the Carthusian order, the rules of St. Francis, free will, human skills, devotion, holiness, whatever you may mention on earth, yes, angelic piety and humility, also God’s Law—all these prove bootless.
This glory is preached and offered to us year after year and day after day. 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). 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?’
Therefore the Holy Spirit must be the Master here and inscribe this knowledge and faith deep in our hearts, must bear witness to our spirit, and say yea and amen to the fact that we have become and eternally remain children of God through faith in Christ (Rom. 8:16).
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.
For this glory, no matter how great and magnificent it may be, is, in the end, consumed by maggots and snakes in the grave. And if those who sit enthroned and exalted here on earth do not depart this life in the knowledge of, and belief in, Christ, they will pass into the hands of the devil; ‘their worm will not die, their fire shall not be quenched’ (Is. 66:24).”
–Martin Luther, Luther’s Works, Vol. 22: Sermons on the Gospel of St. John: Chapters 1-4, ed. Jaroslav Jan Pelikan, Hilton C. Oswald and Helmut T. Lehmann (Saint Louis: Concordia Publishing House, 1999), Jn 1:12.