On Free Will, Holiness and Heresy
There are three things that you should note in the quotations below: 1. The earliest Church fathers believed in libertarian free will. 2. That holiness was Biblical and expected (and therefore some merits and rewards came after salvation). And 3. Their writings were meant to counteract heresy and/or false teaching which sought to divide the earliest Church.
If one wants to challenge these issues as "negating God's sovereignty" (with respect to free will), or "being a works or man based religion" (with respect to free will and holiness) or even claim that opposing views weren't viewed as a heretical problem in the first 300+ years of the Church, you have a great cloud of witnesses to overcome!
IGNATIUS OF ANTIOCH “Be pleasing to him whose soldiers you are, and whose pay you receive. May none of you be found to be a deserter. Let your baptism be your armament, your faith your helmet, your love your spear, your endurance your full suit of armor. Let your works be as your deposited withholdings, so that you may receive the back-pay which has accrued to you” (Letter to Polycarp 6:2 [A.D. 110]).
JUSTIN MARTYR “We have learned from the prophets and we hold it as true that punishments and chastisements and good rewards are distributed according to the merit of each man’s actions. Were this not the case, and were all things to happen according to the decree of fate, there would be nothing at all in our power. If fate decrees that this man is to be good and that one wicked, then neither is the former to be praised nor the latter to be blamed” (First Apology 43 [A.D. 151]).
TATIAN THE SYRIAN “[T]he wicked man is justly punished, having become depraved of himself; and the just man is worthy of praise for his honest deeds, since it was in his free choice that he did not transgress the will of God” (Address to the Greeks 7 [A.D. 170]).
ATHENAGORAS “And we shall make no mistake in saying, that the [goal] of an intelligent life and rational judgment, is to be occupied uninterruptedly with those objects to which the natural reason is chiefly and primarily adapted, and to delight unceasingly in the contemplation of Him Who Is, and of his decrees, notwithstanding that the majority of men, because they are affected too passionately and too violently by things below, pass through life without attaining this object. For . . . the examination relates to individuals, and the reward or punishment of lives ill or well spent is proportioned to the merit of each” (The Resurrection of the Dead 25 [A.D. 178]).
THEOPHILUS OF ANTIOCH “He who gave the mouth for speech and formed the ears for hearing and made eyes for seeing will examine everything and will judge justly, granting recompense to each according to merit. To those who seek immortality by the patient exercise of good works [Rom. 2:7], he will give everlasting life, joy, peace, rest, and all good things, which neither eye has seen nor ear has heard, nor has it entered into the heart of man [1 Cor. 2:9]. For the unbelievers and the contemptuous and for those who do not submit to the truth but assent to iniquity . . . there will be wrath and indignation [Rom. 2:8]” (To Autolycus 1:14 [A.D. 181]).
IRENAEUS “[Paul], an able wrestler, urges us on in the struggle for immortality, so that we may receive a crown and so that we may regard as a precious crown that which we acquire by our own struggle and which does not grow upon us spontaneously. . . . Those things which come to us spontaneously are not loved as much as those which are obtained by anxious care” (Against Heresies 4:37:7 [A.D. 189]).
TERTULLIAN “Again, we [Christians] affirm that a judgment has been ordained by God according to the merits of every man” (To the Nations 19 [A.D. 195]).
“In former times the Jews enjoyed much of God’s favor, when the fathers of their race were noted for their righteousness and faith. So it was that as a people they flourished greatly, and their kingdom attained to a lofty eminence; and so highly blessed were they, that for their instruction God spoke to them in special revelations, pointing out to them beforehand how they should merit his favor and avoid his displeasure” (Apology 21 [A.D. 197]).
“A good deed has God for its debtor [cf. Prov. 19:17], just as also an evil one; for a judge is the rewarder in every case [cf. Rom. 13:3–4]” (Repentance 2:11 [A.D. 203]).
HIPPOLYTUS “Standing before [Christ’s] judgment, all of them, men, angels, and demons, crying out in one voice, shall say: ‘Just is your judgment,’ and the justice of that cry will be apparent in the recompense made to each. To those who have done well, everlasting enjoyment shall be given; while to lovers of evil shall be given eternal punishment” (Against the Greeks 3 [A.D. 212]).
CYPRIAN OF CARTHAGE “The Lord denounces [Christian evildoers], and says, ‘Many shall say to me in that day, Lord, Lord, have we not prophesied in your name, and in your name have cast out devils, and in your name done many wonderful works? And then will I profess unto them, I never knew you: depart from me, you who work iniquity’ [Matt. 7:21–23]. There is need of righteousness, that one may deserve well of God the Judge; we must obey his precepts and warnings, that our merits may receive their reward” (The Unity of the Catholic Church 15, 1st ed. [A.D. 251]).
LACTANTIUS “Let every one train himself to righteousness, mold himself to self-restraint, prepare himself for the contest, equip himself for virtue . . . [and] in his uprightness acknowledge the true and only God, may cast away pleasures, by the attractions of which the lofty soul is depressed to the earth, may hold fast innocence, may be of service to as many as possible, may gain for himself incorruptible treasures by good works, that he may be able, with God for his judge, to gain for the merits of his virtue either the crown of faith, or the reward of immortality” (Epitome of the Divine Institutes 73 [A.D. 317]).
CYRIL OF JERUSALEM “The root of every good work is the hope of the resurrection, for the expectation of a reward nerves the soul to good work. Every laborer is prepared to endure the toils if he looks forward to the reward of these toils” (Catechetical Lectures 18:1 [A.D. 350]).
JEROME “It is our task, according to our different virtues, to prepare for ourselves different rewards. . . . If we were all going to be equal in heaven it would be useless for us to humble ourselves here in order to have a greater place there. . . . Why should virgins persevere? Why should widows toil? Why should married women be content? Let us all sin, and after we repent we shall be the same as the apostles are!” (Against Jovinian 2:32 [A.D. 393]).