John Calvin Commentary Exodus 16:16

"This is the thing which Jehovah hath commanded, Gather ye of it every man according to his eating; an omer a head, according to the number of your persons, shall ye take it, every man for them that are in his tent." — Exodus 16:16 (ASV)

This is the point. The exception¹⁸⁰ follows: that in gathering the food, they were to take account of the Sabbath. A certain daily measure was prescribed, but they were commanded on the day before the Sabbath to lay up twice as much, so that they might observe its rest.

But, unquestionably, God extended His generosity so far as to satisfy them abundantly. It is well known that an omer is the tenth part of an ephah.¹⁸¹ Perhaps we could discover its proportion to the measures now in use among us. However, I am unwilling to dispute regarding an unnecessary point, since we can be sure that what was given was no less than amply sufficient for them.

¹⁸⁰ The rule is here prescribed — the exception does not occur till verse 23.

¹⁸¹ See verse 36. “In Josephus’s time it contained 43 1/5 eggshells, (for the Jews, like many of Oriental nations, reckoned their measures by the contents of middle-sized hens eggs.) But it is by no means probable that during the 1500 years which elapsed from the time of Moses to that of Josephus, the measures of the Hebrews remained the same, there being nothing more liable to change.” — . “In Josephus’s time it contained 43 1/5 eggshells, (for the Jews, like many of Oriental nations, reckoned their measures by the contents of middle-sized hens eggs.) But it is by no means probable that during the 1500 years which elapsed from the time of Moses to that of Josephus, the measures of the Hebrews remained the same, there being nothing more liable to change.” — Rosenmuller..