Upvote:2
To those who believe in the perseverance of the saints, "keeping watch over your souls" does not imply "preventing your soul from falling into eternal damnation." Matthew Henry interprets the phrase this way:
They are to watch against every thing that may be hurtful to the souls of men, and to give them warning of dangerous errors, of the devices of Satan, of approaching judgments; they are to watch for all opportunities of helping the souls of men forward in the way to heaven.
There are many things "hurtful to the souls of men," besides eternal damnation – namely, sin. Jamieson, Fausset, and Brown suggest that the verse teaches that leaders will have to give account not only for their own sins, but for those of their flock. They see this passage as a parallel to Acts 20:28:
Pay careful attention to yourselves and to all the flock, in which the Holy Spirit has made you overseers, to care for the church of God, which he obtained with his own blood. (ESV)
Upvote:4
Because although Christians cannot lose their salvation, they can still appear before the Lord in shame rather than in confidence (1 John 2:28). The good shepherds who watch over the flock want them to enter into the best the Lord has for them, and not be "scarcely saved" (1 Peter 4:17-18). Not all Christians will inherit a crown and rule with Christ; that belongs to the worthy.
So the verse is about obeying the leaders so that they'll be able to give a good testimony of your conduct at the judgment seat of Christ. It appears that the Lord will weigh their words, so let them say you obeyed and not resisted, or it will go bad for you.
For instance, if you look at 2 Peter 1:5-11, we see that continuing in sanctification leads to an abundant entrance into the kingdom. Verse 8 begins with "For if," making it conditional. Otherwise we are shortsighted and are not dealing with sin. God makes a difference, but saves both Christians.