Then Moses, exulting in the safety of his own people, and in the destruction of the enemy, by such a miracle, sang a song of praise to God, and the whole multitude, both of males and females, took part in it. But, after they had entered the desert, and advanced a journey of three days, want of water distressed them; and, when it was found, it proved of no use on account of its bitterness. And then for the first time the stubbornness of the impatient people showed itself, and burst forth against Moses; when, as instructed by God, he cast some wood into the waters, and its power was such that it rendered the taste of the fluid sweet.
Thence advancing, the multitude found at Elim twelve fountains of waters, with seventy palm-trees, and there they encamped. Again the people, complaining of famine, heaped reproaches upon Moses, and longed for the slavery of Egypt, accompanied as it was with abundance to please their appetite, when a flock of quails was divinely sent, and filled the camp. Besides, on the following day, those who had gone forth from the camp perceived that the ground was covered with a sort of pods, the appearance of which was like a coriander-seed of snowy whiteness, as we often see the earth in the winter months covered with the hoar-frost that has been spread over it.
Then the people were informed, through Moses, that this bread had been sent them by the gift of God; that every one should gather in vessels prepared for the purpose only so much of it as would be sufficient for each, according to their number, during one day; but that on the sixth day they should gather double, because it was not lawful to collect it on the Sabbath. The people, however, as they were never prone to obedience, did not, in accordance with human nature, restrain their desires, providing in their stores not merely for one, but also for the following day.
But that which was thus laid up swarmed with worms, while its fetid odor was dreadful, yet that which was laid up on the sixth day with a view to the Sabbath remained quite untainted. The Hebrews made use of this food for forty years; its taste was very like that of honey; and its name is handed down as being manna. Moreover, as an abiding witness to the divine gift, Moses is related to have laid up a full gomer of it in a golden vessel.
Source: Sacred History (New Advent)