From Mircea Eliade’s Zalmoxis, in the chapter The Devil and God: Prehistory of the Romanian Folk Cosmogony. Eliade reports several variants of this story so I’m only giving his ‘base’ version – which I love for the mental image of the final episode.
Before the world was created there was only an unending mass of water, on which God and Satan walked about. When God had decided to create the Earth he sent Satan ‘to the bottom of the sea to take, in God’s name, some of the seed of Earth and bring it back to him on the surface of the water.’ Twice Satan dived to the bottom of the sea, but, instead of taking the seed of Earth in God’s name, as he had been commanded to do, he took it in his own name. While he was rising to the surface all the seed slipped through his fingers. On a third descent to the bottom of the Waters he took the seed in his own name and in God’s. When he returned to the surface, a little mud – this is, the amount he had taken in God’s name – remained under his fingernails; all the rest of it had slipped through his fingers. With the mud that was left under the Devil’s fingernails God made a mount of earth, on which he lay down to rest. Thinking that God was asleep, Satan decided to throw him into the water and drown him, so that he should be left sole lord of the Earth. But the farther Satan rolled God, the more the Earth grew and spread out under him. And so the Earth kept spreading out until there was no more room for the water.”
A Polish version of the last segment goes:
With the sand God made the Earth, but it was barely big enough for the two of them to lie down comfortably. The Devil, seeing that God had fallen asleep, began pushing him toward the sea. But it was to no avail, for the Earth kept enlarging and spreading out under God.