Romans 4:3
Although Abraham was a friend of God, which Scripture specifically mentions three times, it is also clear that he had his lapses of faith. The Bible says that “Abraham believed God, and it was accounted to him for righteousness.” Does this mean that Abraham was declared righteous because of the good things he did? Did God justify Abraham because he lived such a holy, pure, and flawless life? No. Any honest look at the life of Abraham would clearly show that he wasn’t a perfect man.
Having said that, it is also important to point out that although Abraham deviated occasionally from the straight and narrow path, he always came back. If someone says he or she is a Christian but falls away and never returns to the faith, then he or she wasn’t a believer in the first place. As 1 John 2:19 says, “They went out from us, but they were not of us; for if they had been of us, they would have continued with us; but they went out that they might be made manifest, that none of them were of us.”
One of the evidence that you are a child of God is that you feel convicted whenever you sin, and can never be content with living in sin.