Who is obligated to wash the garment?
Ba'al ha'Turim: Even though the command is issued to the Kohen, he is not obligated to actually do the washing, but others are permitted to perform it. 1
See Torah Tamimah, note 226.
Why does the Torah write here "Vechibsu" and in Pasuk 58, "Vehcubas Sheinis ... "?
Yerushalmi Shabbos, 2:1: This teaches us that the first washing requires intent
Why does the Torah add the words "Eis asher bo ha'Nega"?