'Observing The Law' in the Bible

Take these [men] [and] purify yourself along with them and {pay their expenses} so that they can shave [their] heads, and everyone will know that [the things] which they had been informed about you are nothing, but you yourself also agree with observing the law.

"I am a Jew, born in Tarsus, in Cilicia, but raised [here] in this city [i.e., Jerusalem]. [I was] instructed by Gamaliel [i.e., a renowned Jewish rabbi of the time] according to the strictest methods of observing the law of our forefathers. [I was very] eager to serve God, just as all of you are here today.

For no human being can be made upright in the sight of God by observing the Law. All that the Law can do is to make man conscious of sin.

Now this [is another reason for observing the law of love]: You should know that it is about time to wake up out of your [spiritual] sleep, because [the day of our final] salvation is now nearer to us than when we first believed [in Christ].

and to be found in [fellowship with] Him, not having a righteousness of my own, acquired by observing the law of Moses, but one acquired through believing in Christ. This righteousness, which comes from God, is based on faith.