Srimad Bhagavatam Canto 03, Chapter 08, Text 19

SB 3.8.19

sa ittham udviksya tad-abja-nala-
 nadibhir antar-jalam avivesa
narvag-gatas tat-khara-nala-nala-
 nabhim vicinvams tad avindatajah
 
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada: 
 
Lord Brahma, thus contemplating, entered the water through the channel of the stem of the lotus. But in spite of entering the stem and going nearer to the navel of Visnu, he could not trace out the root.
 
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada: 
 
By dint of one’s personal endeavor one may go nearer to the Lord, but without the Lord’s mercy one cannot reach the ultimate point. Such understanding of the Lord is possible only by devotional service, as confirmed in Bhagavad-gita (18.55): bhaktya mam abhijanati yavan yas casmi tattvatah.
Srimad Bhagavatam Canto 03, Chapter 08, Text 18
Srimad Bhagavatam Canto 03, Chapter 08, Text 20