John Gill Commentary Daniel 1:13

"Then let our countenances be looked upon before thee, and the countenance of the youths that eat of the king`s dainties; and as thou seest, deal with thy servants." — Daniel 1:13 (ASV)

Then let our countenances be looked upon before you And be thoroughly examined, whether any alteration is made therein for the worse: and the countenance of the children that eat of the portion of the king's meat; who were either Chaldean youths brought up in this manner; or rather young men of the Jews, who were not so scrupulous as Daniel and his companions, and made no objection to eating the king's food; let their countenances and ours be compared together: and as you see deal with your servants:

if there is no difference, or we are not the worse for abstaining from the king's meat, then grant us our request, and continue to indulge us in this manner; but, if otherwise, do as you will. Daniel, no doubt, in putting the matter on this issue, as it should turn out at the end of ten days, had a revelation or assurance from God how it would be, or he would never have ventured to put it to such a trial.