'Observing The Law' in the Bible

Take these men and observe the ceremony of purification with them, pay their expenses so they can shave their heads [i.e., to signify that they are making a vow] and [then] everyone will know that there is no truth in what people have been told about you, but that you, too, are living properly and observing the law of Moses.

"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.

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.