Srimad Bhagavatam Canto 04, Chapter 24, Text 50

SB 4.24.50

pura-recaka-samvigna-
 vali-valgu-dalodaram
pratisankramayad visvam
 nabhyavarta-gabhiraya
 
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada: 
 
The Lord’s abdomen is beautiful due to three ripples in the flesh. Being so round, His abdomen resembles the leaf of a banyan tree, and when He exhales and inhales, the movement of the ripples appears very, very beautiful. The coils within the navel of the Lord are so deep that it appears that the entire universe sprouted out of it and yet again wishes to go back.
 
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:  
 
The whole universe is born out of the lotus stem which sprouted from the navel of the Lord. Lord Brahma sat on the top of this lotus stem to create the whole universe. The navel of the Lord is so deep and coiling that it appears that the whole universe again wants to withdraw into the navel, being attracted by the Lord’s beauty. The Lord’s navel and the ripples on His belly always increase the beauty of His bodily features. The details of the bodily features of the Lord especially indicate the Personality of Godhead. Impersonalists cannot appreciate the beautiful body of the Lord, which is described in these prayers by Lord Siva. Although the impersonalists are always engaged in the worship of Lord Siva, they are unable to understand the prayers offered by Lord Siva to the bodily features of Lord Visnu. Lord Visnu is known as siva-viriñci-nutam (Bhag. 11.5.33), for He is always worshiped by Lord Brahma and Lord Siva.
Srimad Bhagavatam Canto 04, Chapter 24, Text 49
Srimad Bhagavatam Canto 04, Chapter 24, Text 51