Steadfastness

Where to find scriptural help, regarding steadfastness:

John 8:34-38
Jesus replied, “I tell you the truth, everyone who sins is a slave to sin. Now a slave has no permanent place in the family, but a son belongs to it forever. So if the Son sets you free, you will be free indeed. I know you are Abraham’s descendants. Yet you are ready to kill me, because you have no room for my word. I am telling you what I have seen in the Father’s presence, and you do what you have heard from your father.”