Q. Does one have to honor a Cohen with the mitzva of Vekidashto, to be first when entering a room, or to take food first when no mitzva is being performed?
A. Poskim disagree if the mitzva of Vekidashto applies only to matters of kedusah and holiness, as would seem from the words of the Talmud (Gittin 59b), Sanctify him for all matters of holiness or extends to all occasions.
Maharsho (Nedarim 62a) depends the above on Rashi’s interpretation, that we are dealing even with items that do not have holiness, and the opinion of the Rosh and the Ran that maintain it applies to the distribution of the Lechem Happanim or similar.
Shita Mekubetzes (Nedarim ibid.) adds that the meaning of “Dabar Shebekedusha” refers to important and relevant matters, where honoring someone is significant and not to trivial acts, that don’t carry any esteem or recognition.
Tumim (15: 3) explains that the reason Poskim do not mention to give precedence and priority to a Cohen at judgment time, is because it is not a matter of holiness. Similarly, Pri Megodim (135: 1) writes that the serving of a Cohen first, refers to a seudas mitzva and not to a regular meal.
Horav Shlomo Miller’s Shlit’a opinion is that when possible it is better to honor a Cohen in all occasions when the kavod is meaningful, since according to many this is a Biblical mitzva. One should do so especially if the Cohen can also be regarded as being a Talmid Chacham.
Rabbi A. Bartfeld as revised by Horav Shlomo Miller Shlit’a