The company of the highest knowledge and Truth; the company of a Guru; contact with a person or an assembly of persons who listen to, talk about, and assimilate the Truth. This highest company also takes the form of hearing or reading the words of highest awareness, reflecting on, discussing and assimilating their meaning, meditating on the source of these words, and bringing this awareness into ones daily life.
From Siree Raag Mahala 1, 71, Guru Granth Sahib:
How is the Society of the Saints to be known?
There, the Name of the One Lord is chanted.
The One Name is the Lord's Command; O Nanak, the True Guru has given me this understanding. ||5||