Pleasant speech multiplies friends, and a gracious tongue multiplies courtesies. Let those who are friendly with you be many, but let your advisers be one in a thousand. When you gain friends, gain them through testing, and do not trust them hastily.
For there are friends who are such when it suits them, but they will not stand by you in time of trouble.
And there are friends who change into enemies and tell of the quarrel to your disgrace.
And there are friends who sit at your table, but they will not stand by you in time of trouble.
When you are prosperous, they become your second self, and lord it over your servants; but if you are brought low, they turn against you, and hide themselves from you.
Keep away from your enemies, and be on guard with your friends.
Faithful friends are sturdy shelter; whoever finds one has found a treasure.
Faithful friends are beyond price; no amount can balance their worth.
Faithful friends are life-saving medicine, and those who love the Lord will find them.
Those who love the Lord direct their friendship aright, for as they are, so are their neighbors also.
Source: Wisdom of Sirach 6.5-17