'In Christ' in the Bible

On the other hand, I am writing a new commandment to you, which is true and realized in Christ and in you, because the darkness [of moral blindness] is clearing away and the true Light [the revelation of God in Christ] is already shining.

But the one who habitually hates (works against) his brother [in Christ] is in [spiritual] darkness and is walking in the darkness, and does not know where he is going because the darkness has blinded his eyes.

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.

Everyone who hates (works against) his brother [in Christ] is [at heart] a murderer [by God’s standards]; and you know that no murderer has eternal life abiding in him.

If anyone says, “I love God,” and hates (works against) his [Christian] brother he is a liar; for the one who does not love his brother whom he has seen, cannot love God whom he has not seen.