Charles Spurgeon Commentary 2 Kings 4:4-6

"And thou shalt go in, and shut the door upon thee and upon thy sons, and pour out into all those vessels; and thou shalt set aside that which is full. So she went from him, and shut the door upon her and upon her sons; they brought [the vessels] to her, and she poured out. And it came to pass, when the vessels were full, that she said unto her son, Bring me yet a vessel. And he said unto her, There is not a vessel more. And the oil stayed." — 2 Kings 4:4-6 (ASV)

And when thou art come in, thou shalt shut the door upon thee and upon thy sons, and shalt pour out into all those vessels, and thou shalt set aside that which is full. So she went from him, and shut the door upon her and upon her sons, who brought the vessels to her; and she poured out. And it came to pass, when the vessels were full, that she said unto her son, Bring me yet a vessel. And he said unto her, There is not a vessel more. And the oil stayed.

There was no reason why "the oil stayed" except that there was "not a vessel more" to receive the flowing stream.