We can be saved only one time, because that’s all it takes and there’s no Scriptural evidence of anyone being saved twice.
We know that to be saved, one must come to Christ, for He said “No one comes to the Father except through Me” (Jhn. 14:6). We also know that it requires the drawing of one to Christ, by the Father, for “No man can come to Me, except the Father which hath sent Me draw him” (Jhn. 6:44).
Can anyone who is drawn by the Father, to Christ, refuse to come to Christ? “All that the Father gives Me will come to Me” (Jhn. 6:37). This is, at the least, declaring that all who come to Christ is because of the Father’s drawing, but I believe that it intends that all whom the Father draws “will” come to Christ, because the phrase “gives Me” in v 37 is synonymous with “draw him” in v 44.
Does anyone who comes to Christ for salvation, ever leave Him? “That of all He has given Me I should lose nothing” (Jhn. 6:39).
One can appear to be in Christ by profession, but a said faith is a dead faith. “But someone will say, "You have faith, and I have works." Show me your faith without your works and I will show you my faith by my works” (Jam 2:18).
One can appear to be in Christ by demonstration. “Many will say to Me in that day, 'Lord, Lord, have we not prophesied in Your name, cast out demons in Your name, and done many wonders in Your name? And then I will declare to them, 'I never knew you; depart from Me, you who practice lawlessness” (Mat 7:23).
Abiding in Christ is the evidence of being in Christ, because if they leave, it shows they never were in Christ, regardless of their profession and demonstration. “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” (1Jo 2:19).