Prove thy servants, I beseech thee, ten days - A period which would indicate the probable result of the entire experiment. If during that period there were no indications of diminished health, beauty, or vigour, it would not be unfair to presume that the experiment in behalf of temperance would be successful, and it would not be improper then to ask that it might be continued longer.
And let them give us pulse to eat - Margin, "of pulse that we may eat." Hebrew, "Let them give us of pulse, and we will eat." The word "pulse" with us means leguminous plants with thin seeds; that is, plants with a pericarp, or seed-vessel, of two valves, having the seeds fixed to one suture only. In popular language the "legume" is called a "pod;" as a "pea-pod," or "bean-pod," and the word is commonly applied to peas or beans. The Hebrew word (זרעים zēro‛ı̂ym) would properly have reference to seeds of any kind - from זרע zâra‛, to disperse, to scatter seed, to sow. Then it would refer to plants that bear seed, of all kinds, and would be by no means limited to pulse - as pease or beans. It is rendered by Gesenius, "seed-herbs, greens, vegetables; i. e., vegetable food, such as was eaten in half-fast, opposed to meats and the more delicate kinds of food." The word occurs only here and in Daniel 1:16. It is rendered in the Vulgate, "legumina;" and in the Greek, ἀπὸ τῶν σπερμάτων apo tōn spermatōn - "from seeds." It is not a proper construction to limit this to "pulse," or to suppose that Daniel desired to live solely on pease or beans; but the fair interpretation is to apply it to what grows up from "seeds" - such, probably, as would be sown in a garden, or, as we would now express it, "vegetable diet." It was designed as an experiment - and was a very interesting one - to show the legitimate effect of such a diet in promoting beauty and health, and the result is worthy of special notice as contrasted with a more luxurious mode of life.
And water to drink - This, also, was a most interesting and important experiment, to show that wine was not necessary to produce healthfulness of appearance, or manly strength and beauty. It was an experiment to illustrate the effect of "cold water" as a beverage, made by an interesting group of young men, when surrounded by great temptations, and is, therefore, worthy of particular attention.

Give us pulse to eat - הזרעים hazzeraim, seeds or grain, such as barley, wheat, rye, and peas, etc. Though a vegetable diet might have produced that healthiness of the system in general, and of the countenance particularly, as mentioned here; yet we are to understand that there was an especial blessing of God in this, because this spare diet was taken on a religious account.

Prove thy servants, I beseech thee, (o) ten days; and let them give us (p) pulse to eat, and water to drink.
(o) Meaning that within this space he might have the test, and that no man would be able to know about it: and thus he spoke, being moved by the Spirit of God.
(p) Not that it was a thing abominable to eat dainty meats, and to drink wine, as both before and after they did, but if they would have by this been won to the King, and had refused their own religion, that meat and drink would have been accursed.

Prove thy servants, I beseech thee, ten days, Here Daniel manifestly includes his companions, and makes his request for himself and them; desiring that they might be tried ten days with different sort of food and drink, and see whether any alteration would be made in them for the worse; which was a proper time for such a trial; for in that time it might be reasonably supposed that their food, if it had any bad effect on them, would appear. Saadiah makes these ten days to be the days between the first day of the year and the day of atonement; but without any foundation:
and let them give us pulse to eat, and water to drink; instead of the king's meat, pulse, beans, pease, vetches, lentiles, rice, millet, and the like. The word (d) used signifies anything sown, all kinds of roots, herbs, and fruits; and, instead of wine, water; meat and drink, it may be thought, that persons of such birth and education had not been used to; and yet they preferred these to the king's dainties, by eating and drinking of which their consciences would be in danger of being defiled.
(d) , Sept.; "de seminibus", Montanus; "de sativis", Cocceius.

pulse--The Hebrew expresses any vegetable grown from seeds, that is, vegetable food in general [GESENIUS].