הלכה על שבת 121:17

As an explanation of the matter: since in every place the Torah gives honor to the right, for instance in the service of the Temple, that only the right is valid for the service. And it is so in the sprinkling on the thumb and the big toe in Parashat "Metzora" it is written: "The right [hand/foot]." Also it is so that in all the doings of people — the right is preferred. Therefore, one should dress the right side first. Also therefore, in undressing one should remove the garment on the left first, so that the right will be dressed for longer, since respect of a limb is when it is covered and dressed. Yet, regarding the tying of Tefillin we find that the Torah gave respect to the left, since the Tefillin is tied on the left arm. And thus, everything regarding tying — we give priority to the left. And everything regarding putting on garments — we give priority to the right, and this is according to the Tur and the Shulchan Aruch. And so it is found in Gemara Shabbat (61a) that Rav Nachman Bar Yitzchak said that Mar the son of Revana did so. Yet all of our Rabbis the Rishonim — the Rif, and the Rambam, and the Rosh, and the Mordechai, and the Sefer Mitzvot Gadol (SM"G) — left this idea out completely and didn't mention it at all. And the reason is clear, since after what it says there (ibid): "Rav Ashi says, we see that Rav Kahana was not strict on this matter." See there, and Rav Ashi is a later Amora [and we always follow the later opinions]. (And in the Artzot Ha'Chayim he writes that Mar the son of Revina is the same generation as Rav Ashi, see there. But this is not the case, since here it is Mar the son of "RAVNA", and not "REVINA". And about him Rav Ashi says in Yevamot (22a): "Isn't Mar the son of Ravna signed on it?" [Mar the son of Ravna] was an earlier Amora.. And anyway this idea is mentioned in the Tur and the Shulchan Aruch, since Rav Nachman Bar Yitzchak said: "Someone who is God-fearing should go out...", and it is upon us to uphold the words of the Tur and the Shulchan Aruch.)