The symptoms of a sādhu are that he is tolerant, merciful and friendly to all living entities. He has no enemies, he is peaceful, he abides by the scriptures, and all his characteristics are sublime.
Such a sādhu engages in staunch devotional service to the Lord without deviation. For the sake of the Lord he renounces all other connections, such as family relationships and friendly acquaintances within the world.
Engaged constantly in chanting and hearing about Me, the Supreme Personality of Godhead, the sādhus do not suffer from material miseries because they are always filled with thoughts of My pastimes and activities.
O My mother, O virtuous lady, these are the qualities of great devotees who are free from all attachment. You must seek attachment to such holy men, for this counteracts the pernicious effects of material attachment.
In the association of pure devotees, discussion of the pastimes and activities of the Supreme Personality of Godhead is very pleasing and satisfying to the ear and the heart. By cultivating such knowledge one gradually becomes advanced on the path of liberation, and thereafter he is freed, and his attraction becomes fixed. Then real devotion and devotional service begin.
SRIMAD BHAGAVATAM 3.25.21–25