'Believer' in the Bible

The one who loves and unselfishly seeks the best for his [believing] brother lives in the Light, and in him there is no occasion for stumbling or offense [he does not hurt the cause of Christ or lead others to sin].

By this the children of God and the children of the devil are clearly identified: anyone who does not practice righteousness [who does not seek God’s will in thought, action, and purpose] is not of God, nor is the one who does not [unselfishly] love his [believing] brother.

But whoever has the world’s goods (adequate resources), and sees his brother in need, but has no compassion for him, how does the love of God live in him?

And this commandment we have from Him, that the one who loves God should also [unselfishly] love his brother and seek the best for him.

If anyone sees his brother committing a sin that does not lead to death, he will pray and ask [on the believer’s behalf] and God will for him give life to those whose sin is not leading to death. There is a sin that leads to death; I do not say that one should pray for this [kind of sin].