The most ennobled friendship is when friends help each other to follow the Way of Ascension.…
Receiving human life, one should vow to transcend the rest of mankind and be of aid to men, exhausting his mind for the sake of others, and making this his satisfaction to the end of time.
From the time one is young, he should associate with companions who are upright and not even temporarily be taken in by friends of low character. Just as water will conform to the shape of the vessel that contains it, so will a man follow the good and evil of his companions. That is so true.
Painting "Samurai Spirits" by Tatiana Berg
To prefer friends who are superior to him, and to avoid those who are his inferiors, is the wisdom of the good man.
One should act so that his fellows will not lose confidence in him.
A samurai should be careful and particular when choosing friends.
A samurai must associate only with those companions who are brave, know their duty, and guard their honor.
He who causes inner discord and discouragement in his friend is not a real friend. Real friends should be chosen among the ones you tested.
To give a person one’s opinion and correct his faults is an important thing. It is compassionate and comes first in matters of service. But the way of doing this is extremely difficult.
To discover the good and bad points of a person is an easy thing, and to give an opinion concerning them is easy, too. For the most part, people think that they are being kind by saying the things that others find distasteful or difficult to say. But if it is not received well, they think that there is nothing more to be done. This is completely worthless. It is the same as brining shame to a person by slandering him. It is nothing more than getting it off one’s chest.
To give a person an opinion one must first judge well whether that person is of the disposition to receive it or not. One must become close with him and make sure that he continually trusts one’s word. Approaching subjects that are dear to him, seek the best way to speak and to be well understood.
Judge the occasion, and determine whether it is better by letter or at the time of leave-taking. Praise his good points and use every device to encourage him, perhaps by talking about one’s own faults without touching on his, but so that they will occur to him.
Have him receive this in the way that a man would drink water when his throat is dry, and it will be an opinion that will correct faults.
This is extremely difficult.
Read further in Samurai: Spirit of the Warrior
This an abstract from the chapter "Friendship" from Spirit of the Warrior by A. R. Berg