what about the Christians at corinth, that paul writes to that have left the faith? at one time they believed. as He said, “no one can take them our of my hand”, but that does not cover them leaving Him on their own accord.
I’m sorry, but that’s just wrong. If you can lose your salvation then Christ’s sacrifice is contingent on your ability to “keep it” rather than on what He has done. That is grace - and why we cannot earn salvation. Yes, there is a sanctification process - which is lifelong and SHOWS that we are HIS, but it is NOT to be confused with Justification - which occurs once - based on Christ’s sacrifice for us. If you can lose salvation, that implies you must do something to earn it. You cannot. Christ is either sufficient or He is not. “My sheep hear my voice and they know me.” Once saved always saved is absolutely Biblical and what is found throughout scriptures. (Romans confirms this over and over - for instance 11:6, 3:20). Also see: John 5:24, Ephesians 2:8-10, Hebrews 6:4-9, 1 John 5:13, John 3:15-18, 1 Peter 1:5. For the discussion of losing one’s salvation, and continuing to sin (which some see this Biblical doctrine as endorsing) see: 2 Corinthians 13:5, and 1 Corinthians.
In summary, if one cannot earn salvation and there is nothing one can do to get it, one cannot lose it. Otherwise, as Scripture says, Christ’s sacrifice is deemed insufficient and in so thinking we put Christ to the cross again and again. (See above Hebrews passage).