Charles Spurgeon (from a sermon preached on Oct. 6, 1889):
...there can be no reason in the faultiness of the believer why the Lord should cease to do him good, seeing that he foresaw all the evil that would be in us. No wandering child of God surprises his heavenly Father. He foreknew every sin we should commit: he proposed to do us good notwithstanding all this foreknown iniquity. If, then, he entered into a covenant with us, and began to bless us with all our sin before his mind, nothing new can spring up which can alter the covenant once made with all these drawbacks known and taken into account. There is no scarlet sin which has been omitted, for the Lord has said, "Come now, and let us reason together: though your sins be as scarlet." He entered into a covenant that he would not turn away from us, to do us good; and no circumstance has arisen, or can arise, which was unknown to him when he thus pledged his word of grace.Thanks to Dan for the link.
Moreover, I would have you remember that we are by God at this day viewed in the same light as ever. He saw us at the first as under sin, fallen and depraved, and yet he promised to do us good.
"He saw me ruined in the fall, yet loved me notwithstanding all."
And if to-day I am sinful, if to-day I have to groan by reason of my evil nature, yet I am but where I was when he chose me, and called me, and redeemed me by the blood of his Son. "When we were yet without strength, in due time Christ died for the ungodly." We were undeserving objects upon whom he bestowed his mercy, out of no motive but that which he drew from his own nature; and if we are undeserving still, his grace is still the same. If it be so, that he still deals with us in the way of grace, it is evident that he still views us as undeserving; and why should he not do good towards us now as he did at the first? Assuredly, the fountain being the same, the stream will continue to flow.
Beloved, we feel sure that he will not cease to bless us, because we have proved that even when he has hidden his face he has not turned away from doing us good. The Lord has withdrawn the light of his countenance, but never the love of his heart. When the Lord has turned away his face from his people, it has been to do them good, by making them sick of self and eager for his love. How often he has brought us back from wandering by making us feel the evil of the sin which grieves his Spirit! When we have cried, "Oh, that I knew where I might find him!" we have been greatly blessed by the anguish of our search. Bear me witness, ye tried people of God; the Lord's chastenings have always been for your good. When the Lord has bruised you till the wound has been blue, your heart has been bettered. When the Lord has taken away your comforts, he has done you good by driving you closer to the highest good. The Lord has enriched you by your losses, and made you healthy by your sicknesses. If, then, the Lord our God, when he is seen in darkest colours, has not turned away from doing us good, we are persuaded that he will never cease daily to load us with benefits.”
Moreover, remember that he sees us now in Christ. Behold, he has put his people into the hands of his dear Son. He has even put us into Christ's body; "for we are members of his body, of his flesh, and of his bones." He sees us in Christ to have died, in him to have been buried, and in him to have risen again. As the Lord Jesus Christ is well-pleasing to the Father, so in him are we well-pleasing to the Father also; for our being in him identifies us with him. If, then, our acceptance with God stands on the footing of Christ's acceptance with God, it standeth firmly, and is an unchanging argument with the Lord God for doing us good. If we stood before God in our own individual righteousness, our ruin would be sure and speedy; but in Jesus our life is hid beyond peril. Firmly believe that until the Lord rejects Christ he cannot reject his people; until he repudiates the atonement and the resurrection, he cannot cast away any of those with whom he has entered into covenant in the Lord Jesus Christ.
...The cost to which our Lord has gone assures us that he will complete his designs of grace.”