“Friendship is agreement in things human and divine, with good will and charity.”

"How many martyrs laid down their lives for the brethren? 

How many spared neither cost nor toil nor their bodies’ torture? 

I suppose that often, not without tears, you have read of that maiden of Antioch who was delivered from among prostitutes by the glorious deceit of a soldier, who became her companion in martyrdom after having found himself the guardian of her virginity in the brothel.

I could cite for you many examples of such heroism, if sheer numbers did not prohibit it and the mass of material impose silence on me. For Christ Jesus preached and spoke, and they were multiplied beyond counting.  He also said,“no one has greater love than to lay down his life for his friends.”

Now the spiritual, which we call true friendship, is desired not with an eye to any worldly profit or for any extraneous reason, but for its own natural worth and for the emotion of the human heart, so that its fruit and reward is nothing but itself. 

Hence our Lord says in the Gospel,“I appointed you to go and to bear fruit,” that is, to “love one another.”

For one goes by making progress in this true friendship, and one bears fruit by savoring the sweetness of its perfection. 

So spiritual friendship is begotten among the righteous by likeness of life, habits, and interests, that is, by agreement in things human and divine, with good will and charity."

Cicero,Amic 8.26.