Investigation in forming Friendships - The Essentials of a State - WEALTH - Tirukkural

791
To make an untried man your friend is ruin sure;
For friendship formed unbroken must endure.
As those who are of a friendly nature will not forsake (a friend) after once loving (him), there is no evil so great as contracting a friendship without due inquiry.

792
Alliance with the man you have not proved and proved again,
In length of days will give you mortal pain.
The friendship contracted by him who has not made repeated inquiry will in the end grieve (him) to death.

793
Temper, descent, defects, associations free
From blame: know these, then let the man be friend to thee.
Make friendship (with one) after ascertaining (his) character, birth, defects and the whole of one's relations.

794
Who, born of noble race, from guilt would shrink with shame,
Pay any price so you as friend that man may claim.
The friendship of one who belongs to a (good) family and is afraid of (being charged with) guilt, is worth even purchasing.

795
Make them your chosen friend whose words repentance move,
With power prescription's path to show, while evil they reprove.
You should examine and secure the friendship of those who can speak so as to make you weep over a crime (before its commission) or rebuke you severely (after you have done it) and are able to teach you (the ways of) the world.

796
Ruin itself one blessing lends:
'Tis staff that measures out one's friends.
Even in ruin there is some good; (for) it is a rod by which one may measure fully (the affection of one's) relations.

797
'Tis gain to any man, the sages say,
Friendship of fools to put away.
It is indead a gain for one to renounce the friendship of fools.

798
Think not the thoughts that dwarf the soul; nor take
For friends the men who friends in time of grief forsake.
Do not think of things that discourage your mind, nor contract friendship with those who would forsake you in adversity.

799
Of friends deserting us on ruin's brink,
'Tis torture e'en in life's last hour to think.
The very thought of the friendship of those who have deserted one at the approach of adversity will burn one's mind at the time of death.

800
Cling to the friendship of the spotless one's; whate'er you pay.
Renounce alliance with the men of evil way.
Continue to enjoy the friendship of the pure; (but) renounce even with a gift, the friendship of those who do not agree (with the world).