Srimad Bhagavatam Canto 03, Chapter 08, Text 22

SB 3.8.22

kalena so ’jah purusayusabhi-
 pravrtta-yogena virudha-bodhah
svayam tad antar-hrdaye ’vabhatam
 apasyatapasyata yan na purvam
 
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada: 
 
At the end of Brahma’s one hundred years, when his meditation was complete, he developed the required knowledge, and as a result he could see in his heart the Supreme within himself, whom he could not see before with the greatest endeavor.
 
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada: 
 
The Supreme Lord can be experienced only through the process of devotional service and not by one’s personal endeavor in mental speculation. The age of Brahma is calculated in terms of divya years, which are distinct from the solar years of human beings. The divya years are calculated in Bhagavad-gita (8.17): sahasra-yuga-paryantam ahar yad brahmano viduh. Brahma’s one day is equal to one thousand times the aggregate of the four yugas (calculated to be 4,300,000 years). On that basis, Brahma meditated for one hundred years before he could understand the supreme cause of all causes, and then he wrote the Brahma-samhita, which is approved and recognized by Lord Caitanya and in which he sings, govindam adi-purusam tam aham bhajami. One has to wait for the mercy of the Lord before one can either render service unto Him or know Him as He is.
Srimad Bhagavatam Canto 03, Chapter 08, Text 21
Srimad Bhagavatam Canto 03, Chapter 08, Text 23