Saint Augustine is considered by many Protestants of the reformed camp (particularly Calvinists) as one of the founders of the Reformation. His teachings about salvation through divine grace are influential to theologians, past and present.
The following is an excerpt from Augustine's Confessions, an autobiographical work, from chapter V:
"Which thing I was sighing for, bound as I was, not with another's irons, but by my own iron will. My will the enemy held, and thence had made a chain for me, and bound me. For of a forward will, was a lust made; and a lust served, became custom; and custom not resisted, became necessity. By which links, as it were, joined together (whence I called it a chain) a hard bondage held me enthralled.
But that new will which had begun to be in me, freely to serve Thee, and to wish to enjoy Thee, O God, the only assured pleasantness, was not yet able to overcome my former wilfulness, strengthened by age. Thus did my two wills, one new, and the other old, one carnal, the other spiritual, struggle within me; and by their discord, undid my soul.
Thus, I understood, by my own experience, what I had read, how the flesh lusteth against the spirit and the spirit against the flesh. Myself verily either way; yet more myself, in that which I approved in myself, than in that which in myself I disapproved. For in this last, it was now for the more part not myself, because in much I rather endured against my will, than acted willingly. And yet it was through me that custom had obtained this power of warring against me, because I had come willingly, whither I willed not.And who has any right to speak against it, if just punishment follow the sinner? Nor had I now any longer my former plea, that I therefore as yet hesitated to be above the world and serve Thee, for that the truth was not altogether ascertained to me; for now it too was. But I still under service to the earth, refused to fight under Thy banner, and feared as much to be freed of all incumbrances, as we should fear to be encumbered with it.Thus with the baggage of this present world was I held down pleasantly, as in sleep: and the thoughts wherein I meditated on Thee were like the efforts of such as would awake, who yet overcome with a heavy drowsiness, are again drenched therein.
And as no one would sleep for ever, and in all men's sober judgment waking is better, yet a man for the most part, feeling a heavy lethargy in all his limbs, defers to shake off sleep, and though half displeased, yet, even after it is time to rise, with pleasure yields to it, so was I assured that much better were it for me to give myself up to Thy charity, than to give myself over to mine own cupidity; but though the former course satisfied me and gained the mastery, the latter pleased me and held me mastered.Nor had I any thing to answer Thee calling to me, Awake, thou that sleepest, and arise from the dead, and Christ shall give thee light. And when Thou didst on all sides show me that what Thou saidst was true, I, convicted by the truth, had nothing at all to answer, but only those dull and drowsy words, “Anon, anon,” “presently,” “leave me but a little.”
But “presently, presently,” had no present, and my “little while” went on for a long while; in vain I delighted in Thy law according to the inner man, when another law in my members rebelled against the law of my mind, and led me captive under the law of sin which was in my members.For the law of sin is the violence of custom, whereby the mind is drawn and holden, even against its will; but deservedly, for that it willingly fell into it.Who then should deliver me thus wretched from the body of this death, but Thy grace only, through Jesus Christ our Lord."