As Christians, we hear and talk a lot about "repentance". And well we should, it is a very important term. But we tend to take it for granted, without putting too much thought into what it actually means. What is repentance? Is it necessary to repent to be saved? These are questions to which you will get some very confusing answers, in amongst a variety of stutters.
Perhaps the main reason for this is that, especially in our culture, the term has more than one meaning. There's general repentance, and specific repentance. Specific repentance, as the term implies, involves specific instances of sin during your Christian life. It might be a one time thing. You sin, you repent. It might be a longstanding thing. You sin, you keep sinning, then finally you realise you've been sinning this whole time, you repent. General repentance is much broader. This is a full change of heart and mind towards sin as a whole. You live for sin, you hear the Gospel, you repent of your sin and live for Christ.
Throughout your faith, you will hear both uses quite frequently. But they both have different implications. On the one hand, specific repentance is neither necessary, nor even indicative of salvation. To go through every single one of your transgressions and repent isn't even practical. You're not even going to remember every time you've fallen short of God's Holy standard, much less be able to repent of them all.
Furthermore, as Scripture says, there is a difference between "worldly" and "Godly" sorrow (2 Corinthians 7:10). "For godly sorrow produces repentance leading to salvation, not to be regretted; but the sorrow of the world produces death."
The great irony is even the world understands this concept. We've all been told "you're only sorry you got caught". This is what worldly sorrow looks like. Worldly sorrow, and the specific repentance it may bring, is not a change of attitude towards sin and God. It might prompt one to act penitent, but when God looks at the heart, He still sees the same old sinner, like a biting dog wearing a muzzle. Remove the muzzle, repeat the sin.
But Paul says Godly sorrow produces repentance, leading to salvation. This is far from the only time repentance and salvation are mentioned together, so much so that one must accept one simple fact: Repentance is necessary for salvation.
But how can this be? The standard objection, and the most understandable one, is that salvation is by grace, through faith, not of works. This objection only holds up, however, when we erroneously categorise repentance as a work. In reality, repentance and faith are inseparable.
The key to understanding this is that it is illogical to place your faith in Christ as Savior without recognising that you need salvation. Remember, what we have termed "general repentance" is a change of mind towards sin. It is the recognition that your way is the wrong way, and the desire to instead go God's way.
So we see that repentance is not a work that brings us salvation, but rather is effectively one half of faith. It is the recognition that sin is bad, and to therefore turn away from it. The natural result of this, of course, is that turning away. When you recognise that West is the wrong direction, and you need to go East, do you turn East and keep walking backwards towards the West? Or do you even stay seated where you are, knowing you're in the wrong place, but making no effort to go the right way?
The relationship between faith, works, salvation, and repentance, cannot be neglected. The reason Paul can say, in one place, that repentance leads to salvation, while in another place saying that we are saved by grace, through faith, not of works, is because faith and repentance are two sides of the same coin. Faith and repentance lead to salvation, then salvation leads to works. Works are the evidence of salvation. Thus, faith and repentance are demonstrable things.
We see this throughout Scripture. Sinners are brought to faith, they suddenly realise their sorry state, they change automatically, not as a means of getting saved, but often even as an outward display of gratitude for salvation earned.
Paul is the most obvious example of this. Being, by his own admission, the chief of sinners (1 Timothy 1:15), he actually labored harder for the Gospel than the rest of the Apostles (1 Corinthians 15:10). This is how he demonstrated his repentance.
So, in short, there are two kinds of repentance. General repentance, a change of mind towards sin and God, is necessary for salvation. This is not a work, but one side of the coin of faith. Specific repentance is more within the works category, being specific actions relating to specific sins. This is neither necessary for, nor indicative of, salvation.