Bhagavad Gita: Those who are purely in Krsna consciousness and do not know anything other than Krsna, called Mahatma. (The Most Confidential Knowledge, Text 15, Chapter 9)

Sri-bhagavan uvaca

jnana-yajnena capy anye
yajanto mam upasate
ekatvena prthaktvena
bahudha visvato-mukham

 (The Most Confidential Knowledge, Text 15, Chapter 9)

Meaning: Others, who engage in sacrifice by the cultivation of knowledge, worship the Supreme Lord as the one without a second, as diverse in many, and in the universal form.

Bhagavad Gita: Those who are purely in Krsna consciousness and do not know anything other than Krsna, called Mahatma.  (The Most Confidential Knowledge, Text 15, Chapter 9)