SB 8.19.34

kramato gāṁ padaikena
 dvitīyena divaṁ vibhoḥ
khaṁ ca kāyena mahatā
 tārtīyasya kuto gatiḥ
Synonyms: 
kramataḥ — gradually; gām — the surface of the land; padā ekena — by one step; dvitīyena — by the second step; divam — the whole of outer space; vibhoḥ — of the universal form; kham ca — the sky also; kāyena — by the expansion of His transcendental body; mahatā — by the universal form; tārtīyasya — as far as the third step is concerned; kutaḥ — where is; gatiḥ — to keep His step.
Translation: 
Vāmanadeva will first occupy the three worlds with one step, then He will take His second step and occupy everything in outer space, and then He will expand His universal body to occupy everything. Where will you offer Him the third step?
Purport: 

Śukrācārya wanted to tell Bali Mahārāja how he would be cheated by Lord Vāmana. “You have promised three steps,” he said. “But with only two steps, all your possessions will be finished. How then will you give Him a place for His third step?” Śukrācārya did not know how the Lord protects His devotee. The devotee must risk everything in his possession for the service of the Lord, but he is always protected and never defeated. By materialistic calculations, Śukrācārya thought that Bali Mahārāja would under no circumstances be able to keep his promise to the brahmacārī, Lord Vāmanadeva.