All that the Father giveth Me shall come to Me; and him that cometh to Me I will in no wise cast out. – John 6:37

If a man believeth in Christ with all his heart, his salvation is secure beyond hazard; and I always look upon this as the very jewel of the crown of salvation, that it be irreversible.

“His honor is engaged to save
The meanest of His sheep.
All that His heavenly Father gave
His hands securely keep.

God does not make you His child to-day, and turn you out to-morrow; He does not forgive you to-day, and then punish you the next day. As true as God is God, if thou gettest thy pardon, the earth may melt away just as a moment’s foam dissolves into the wave that bears it and is lost for ever; the great universe may pass away and be like the hoar-frost before the morning sun; but thou never canst be condemned. As long as God is God, he who has got his pardon signed and sealed, is beyond the reach of harm. I would not preach any other-I dare not. It would not be worth your receiving, it would not be worth my taking the trouble to preach; but this is worth any man’s having indeed, for it is a sure investment. He who puts himself into the hands of Christ has a sure keeper, come what may-and there may come strong temptations and strong affections, and there may come strong pains and hard duties, but He that hath helped us bears us through, and makes us more than conquerors too. Oh! to be pardoned once, with the certain assurance that we shall be pardoned for ever, beyond the hazard of being cast away! ~ C.H. Spurgeon

https://www.blueletterbible.org/Comm/spurgeon_charles/sermons/0199.cfm