Now, undoubtedly, He is the good God who “sends rain on the just and on the unjust, and makes His sun to rise on the evil and on the good;” Matthew 5:45 sustaining and nourishing and assisting even Marcionites themselves! [Tertullian Adv Marc. 4.36]
Marcion, a very mouthpiece of ungodliness ; for one who teaches different Gods, one good, the other just, contradicts the Son, who says Rigtheous Father [John 17.25]. Again, one who says that the Father is different from the Maker of the world, is at variance with the Son who says, If then God so clothe the grass, which is to-day in the to-morrow is cast into the oven [Luke 12.8]; and Who maketh His sun to rise on the evil and on the good, and sendeth rain on the just and on the unjust. [Matt 5:45] This Marcion, then, came next, the originator of another error; for being refuted by the texts from the Old Testament which are cited in the New, he who had already effaced the idea of God, was the first to venture also on cutting out those very testimonies to the word of faith preached in the Gospel ; and to consent to weaken the Church's faith, as though there had been no heralds of it. [Cyril of Jerusalem Catechetical Lecture 6:15]
Marcion, therefore, himself, by dividing God into two, maintaining one to be good and the other judicial, does in fact, on both sides, put an end to deity. For he that is the judicial one, if he be not good, is not God, because he from whom goodness is absent is no God at all; and again, he who is good, if he has no judicial power, suffers the same [loss] as the former, by being deprived of his character of deity. And how can they call the Father of all wise, if they do not assign to Him a judicial faculty? For if He is wise, He is also one who tests [others]; but the judicial power belongs to him who tests, and justice follows the judicial faculty, that it may reach a just conclusion; justice calls forth judgment, and judgment, when it is executed with justice, will pass on to wisdom. Therefore the Father will excel in wisdom all human and angelic wisdom, because He is Lord, and Judge, and the Just One, and Ruler over all. For He is good, and merciful, and patient, and saves whom He ought: nor does goodness desert Him in the exercise of justice, nor is His wisdom lessened; for He saves those whom He should save, and judges those worthy of judgment. Neither does He show Himself unmercifully just; for His goodness, no doubt, goes on before, and takes precedency. The God, therefore, who does benevolently cause His sun to rise upon all, and sends rain upon the just and unjust, shall judge those who, enjoying His equally distributed kindness, have led lives not corresponding to the dignity of His bounty; but who have spent their days in wantonness and luxury, in opposition to His benevolence, and have, moreover, even blasphemed Him who has conferred so great benefits upon them. [Irenaeus Adv Haer 3.25.3,4] For God the Lord and Demiurge, in caring for all, makes his sun rise on evil and good, sends his rain on those who blaspheme and those who glorify him, and nourishes all. [Epiphanius Against the Marcionite Sectarians of Lucian] And, to prove that the just man belongs in the category of goodness, he said, 'Be ye like unto your Father which is in heaven, for he maketh his sun to rise on good and evil, and sendeth rain on just and unjust,'32 to make it plain that just is good and good is just, and that evil is unjust, and unjust, evil. [Epiphanius Against the Ptolemaeans]There can be no doubt that an early writer before Irenaeus 'alerted' the world to Marcion's editing of Matt 5:45 out of the gospel. It is probably Tertullian's source and likely saw Luke 6:35 immediately followed by Matt 5:45. This sounds like Justin's harmonized gospel from what I can remember. Justin I think witnesses sayings 'harmonized' in this way. Is Justin the source?