'Necessary' in the Bible

Finally therefore, brothers, we ask you and appeal to [you] in the Lord Jesus that, just as you have received from us how it is necessary for you to live and to please God, just as indeed you are living, that you progress even more.

But about loving the brothers, there is no need for me to say anything to you in this letter: for you have the teaching of God that love for one another is right and necessary;