Peter ends this section dealing with “honorable conduct” that dealt mostly with the way we are to be respectful and submissive in our behavior, by encouraging five qualities:
Unity of mind does not mean that all believers should think the same thoughts, or march in lock-step to one “approved” interpretation of things, but rather to the mindset of unity. That is where we respect and love each other, sharing life including conversations about what we think.
Sympathy ties into that. We feel for each other. We take others’ perspectives and positions into account. We love each other from a position of understanding.
Brotherly love is the act of considering others and their needs as higher than our own. We focus on what we can do for each other, not what we can get for ourselves.
A tender heart is one that seeks the gentle way of helping others. Think someone is in the wrong? The tender heart nudges and encourages, it doesn’t judge and impose.
A humble mind, once again, is more about mindset. The humble mind is the wise one. The one who knows enough to know that it doesn’t. The fool is he who thinks he doesn’t have anything to learn.
So, once again, this description from Peter as to what the right conduct from a believer should be points to a deferment, a respect, a submissive approach to relationships.