One of the reasons so many people have difficulty with the notion that Christians are obligated to keep God’s commandments is that they think that keeping commandments is contrary to salvation by grace. But the problem is really one of ignorance regarding the clear teaching of the Bible.
We must begin with the fact that the Bible teaches salvation by grace–that is, salvation is the work of God, not of men. You could never earn salvation. No matter how much you do, you will never deserve the favor of God. “By grace you have been saved…; not of works” (Ephesians 2:8-9; cf. Titus 3:5). Give up every notion that you can ever even add to the worth and merit of Christ’s work, let alone save yourself.
At the same time, the Bible clearly teaches that Christians are under obligation to keep God’s laws and commands. It teaches this when it gives us commands instead of suggestions, when it makes demands instead of requests, when it prohibits things instead of simply warning against them, when it makes threats and lays down conditions instead of telling us what a nice thing it would be if we could find it in our hearts to do what is pleasing to God. Consider these statements: “If you love me, keep my commandments” (John 14:15); “He who says, ‘I know Him,’ and does not keep His commandments, is a liar, and the truth is not in him” (1John 2:4). If you know your Bible at all, you know that these are not rare statements, but statements that are characteristic of the New Testament.
The Bible teaches that salvation is by grace alone. It also teaches that Christians must obey God’s commandments. The problem is not that there is a contradiction in the Scriptures. The problem may be that our Pharisaic hearts do not like the thought that we are obliged to do things for which we receive no credit! May God enable us all to believe the truth–the whole truth–and love it.