Sabbath 25b: “For Rav Yehuda said in the name of Rav: This was the practice of Rabbi Yehuda bar Ilai: on Sabbath eve they would bring him a basin full of hot water, and he would wash his face, hands, and feet, and wrap himself and sit in tasseled linen sheets, and he looked like an angel of the Lord of Hosts.” And Rashi explained (Kiddushin 72a): “And they are like ministering angels — dressed in white and wrapped like ministering angels. And it is written (Ezekiel 9): ‘and the man clothed in linen.’ And similarly we say in Bameh Madlikin (Sabbath 25b) about Rabbi Yehuda, that he would wrap himself and sit in tasseled sheets and looked like an angel, etc. And in Nedarim 20b we also say: Who are the ministering angels? The sages. And why are they called ministering angels? Because they are distinguished like ministering angels in fine clothing.”

Dressed in white like angels includes white pants too (apparently that’s how angels dress) and nothing black. As is the custom among the kabbalists.

I think the white (= transparent?) is the angels’ bodies, not their clothing. To be dressed like an angel means to be naked.

“the man clothed in linen”

“Angel” has the numerical value of “white garment” — 91 — and they left room for me to distinguish myself, by the merit of my holy forefathers, may their resting place be Eden.

Just like we learn modesty from a cat, and then the most modest thing would be to be naked. On the Sabbath all the more so.