Srimad Bhagavatam Canto 08, Chapter 21, Text 05

SB 8.21.5

brahmadayo loka-nathah
 sva-nathaya samadrtah
sanuga balim ajahruh
 sanksiptatma-vibhutaye
 
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada: 
 
Lord Brahma and all the predominating deities of the various planetary systems began to worship Lord Vamanadeva, their supreme master, who had reduced Himself from His all-pervading form to His original form. They collected all the ingredients and paraphernalia for this worship.
 
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada: 
 
Vamanadeva first expanded Himself to the universal form and then reduced Himself to the original Vamana-rupa. Thus He acted exactly like Lord Krsna, who, at the request of Arjuna, first showed His universal form and later resumed His original form as Krsna. The Lord can assume any form He likes, but His original form is that of Krsna (krsnas tu bhagavan svayam). According to the capacity of the devotee, the Lord assumes various forms so that the devotee can handle Him. This is His causeless mercy. When Lord Vamanadeva resumed His original form, Lord Brahma and his associates collected various paraphernalia for worship with which to please Him.
Srimad Bhagavatam Canto 08, Chapter 21, Text 04
Srimad Bhagavatam Canto 08, Chapter 21, Text 06-07