In the fifteenth incarnation, the Lord assumed the form of a dwarf brāhmaṇa [Vāmana] and visited the arena of sacrifice arranged by Mahārāja Bali. Although at heart He was willing to regain the kingdom of the three planetary systems, He simply asked for a donation of three steps of land.
Srimad Bhagavata Purana
श्रीमद्भागवतमहापुराणम्
मूल श्लोकः
पञ्चदशं वामनकं कृत्वागादध्वरं बलेः । पदत्रयं याचमानः प्रत्यादित्सुस्त्रिविष्टपम्
pañcadaśaṃ vāmanakaṃ kṛtvāgādadhvaraṃ baleḥ | padatrayaṃ yācamānaḥ pratyāditsustriviṣṭapam
SB 1.3.19