“Do not be afraid,” He says. “From now on you will catch men” [Luke 5:10].
[Jesus] not only gives poor, frightened Peter consolation with these kind words, with which He grants him His grace and gives him absolution, but He also continues to strengthen this consolation with a great promise. He promises that He will give to him and accomplish in him still much more and greater than he has previously received from Him, so that he would have to perceive and learn His heart and love toward him. “From now on,” He says, “you will catch men” [Luke 5:10]. This is a rich consolation and gracious gift, so that he is not frightened because of his unworthiness and sins. He will not only have the forgiveness of sins but also will know that God wants to carry out much greater things through him, so that he is also a consolation and a help to others.
“This catch of fish which you have made,” He means to say, “is much too little and nothing. Henceforth you will become a different fisherman, in a different sea, with a different net and boat. I want to put you into the office which is called ‘catching men,’ that is, bringing souls throughout the wide world out of the devil’s power into God’s kingdom. That is when you will begin to be a useful man who can help all people, just as you have been helped.”
So from this Gospel reading let us truly learn and grasp Christ and the power of His consolation, so that we can console both ourselves and others. We should teach and remind consciences that are in distress and fright by no means to run away and flee from Christ, but rather to flee to Him and expect His consolation. Such fleeing and being frightened is nothing else than chasing your own salvation and blessedness away from you. He is never present in order to frighten, but only to take your sin and distress away from you. He also does not approach you and follow after you in order to put you to flight, but in order kindly to attract you to Himself.
Therefore, you must not do Him the dishonor of beating Him away from you or of wanting to turn the consolation He brings you into fright and despair, but much rather of running to Him with all confidence. Then you will soon hear the cheerful, consoling words (“Do not be afraid” [Luke 5:10]) which He sincerely speaks to you and all troubled consciences, to absolve us from all sins and to take away all fright. Yes, He will in addition bless you much more abundantly, so that you become a holy, blessed, and useful person in His kingdom, able to console and bring to Him other people who, like you, are now frightened and in need of consolation and grace.
Thus you see how a person comes out of spiritual poverty and distress, that is, obtains the forgiveness of sins and peace of conscience through these words of Christ, and in addition grace and the increase of spiritual gifts, without any of his own merit and worthiness but only from the grace of Christ. Similarly, they did not obtain the physical miracle of catching fish because of their work; it was not given to them until they had first lost their work and labor and had despaired. However, just as He there does not forbid their work, but first tells them to throw out their nets for a catch, so here He does not want to abolish the works. Even though St. Peter does not merit grace and forgiveness through them—it is given to him for nothing—He still does not want him to go on without work and effort. Yes, He imposes on him the office and work of bringing it to other people. Because He imposes on him this office, He gives him the consolation that He will also give him strength and blessing for it. “For I,” He says, “will make you into a fisher of men” [Luke 5:10]. Thus both are taught correctly, namely, that faith merits nothing through works, and yet does all kinds of works in its estate and office according to God’s Word and command.
Christ Himself shows the meaning of this history of St. Peter’s catch of fish when He says, “From now on you will catch men” [Luke 5:10]. This represents the spiritual governance of the Church, which consists of the preaching office. The sea or water is the world, the fish are people, the hand and the net with which the fish are pulled in is the external preaching office. Just as the net is thrown out among the water, so the preaching goes out among the people.
Martin Luther, “Gospel for the Fifth Sunday after Trinity,” in Luther’s Works, ed. Benjamin T. G. Mayes, James L. Langebartels, and Christopher Boyd Brown, vol. 78 (Saint Louis, MO: Concordia Publishing House, 2015), 218–220.