Some of them left of it; either distrusting God's providence for their future provisions; or out of curiosity to learn the nature of this manna, and what they might do when occasion required. It stank, not so much from its own nature, which was pure and durable, as from God's judgment.
Related Commentaries of Exodus 16:20
Exodus 16:20
20 Notwithstanding they hearkened not unto Moses; but some of them left of it until the morning, and it bred worms, and stank: and Moses was wroth with them.