And not only so, but we glory in tribulations also: knowing that tribulation worketh patience; And patience, experience; and experience, hope: And hope maketh not ashamed; because the love of God is shed abroad in our hearts by the Holy Ghost which is given unto us. Romans 5:3-5

   Knowing that tribulation worketh patience (5:3). He who has faith indeed has all the excellent things (which are mentioned in the text), but in a hidden way. Through tribulation they are tried and purified to the highest degree. Whatever (virtues) tribulation finds in us, it develops more fully. If anyone is carnal, weak, blind, wicked, irascible, haughty, and so forth, tribulation will make him more carnal, weak, blind, wicked and irritable. On the other hand, if one is spiritual, strong, wise, pious, gentle and humble, he will become more spiritual, wise, pious, gentle, and humble, as the Psalmist says in Psalm 4:1: “Thou hast enlarged me when in was in distress.”
   Those speak foolishly who ascribe their anger or their impatience to such as offend them or to tribulation. Tribulation does not make people impatient, but proves that they are impatient. So everyone may learn from tribulation how his heart is constituted.
   Those are ignorant, childish and indeed hypocritical who outwardly venerate the relics of the holy Cross, yet flee and detest tribulation and affliction. Holy Scripture calls tribulation the cross of Christ in a special sense, as in Mathew 10:38: “He that taketh his not cross, and followeth after me, is not worthy of me.” Let everyone be sure that he is not Christian but a Turk and an enemy of Christ who refuses to bear this cross; for here the Apostle speaks of all (believers) when he says: “We glory in tribulations.” And in Acts 14:22 we read: “We must through much tribulation enter the kingdom of God.” “Must” does not mean that tribulation comes by chance, or that it is a matter of choice for us, of that we may take it or leave it. In many Scripture passages our Lord is called a “Savior” and a “Helper in need,” and this means that all who do not desire to endure tribulation, rob him of his titles and names of honor. To such people our Lord will never become a Savior, because they do not admit that they are under condemnation. To them God is never mighty, wise and gracious, because they do not desire to honor Him as creatures that are weak, foolish and subject to punishment.

—Martin Luther, Commentary on Romans, trans. J. Theodore Mueller (Grand Rapids, Zondervan, 1954), 74–75.