For the Lord will not cast off forever. — Lamentations 3:31
God didn't reject his people, which he foreknew. — Romans 11:2

Author
Charles Spurgeon
Summary: The Lord may seem to cast us off for a time, but He will never do so forever. His love is not fickle: He chose us from eternity, died for us, and will love us for all eternity. The believer’s salvation is bound up with His honor; Jesus does not abandon those who are His, just as the head does not cast off its members or a husband his wife. If we fear that we have been cast off, we must reject that thought and remember that God has not cast off the people He knew beforehand.
He might cast us off for a time, but not forever. A woman might do without her ornaments for a few days, but she will not forget them or throw them onto the rubbish heap. The Lord is not in the habit of casting off those whom He loves: for ‘having loved His own who were in the world, He loved them to the end.’
Some speak of being in grace or out of grace, as though we were rabbits going in and out of their burrows: but, in truth, it is not so. The Lord’s love is a more serious and lasting matter than that.
He chose us from eternity, and He will love us throughout all eternity. He loved us enough to die for us, and therefore we can be sure that His love will never die. His honor is so bound up with the believer’s salvation that He could no more cast the believer off than He could cast off His own robes befitting His office as King of glory. No, no! The Lord Jesus, as Head, never casts off His members; as Husband, He never casts off His wife.
Did you think you had been cast off? Why did you think so ill of the Lord who has betrothed you to Himself? Cast off such thoughts, and never allow them to lodge in your soul again. “God has not cast away His people whom He foreknew.” (Romans 11:2) “He hates divorce.” (Malachi 2:16).
Source: The Chequebook of the Bank of Faith. Translation by Allan Roman.
http://www.spurgeon.com.mx/chequera/meditames/enero.pdf