Washing Once or Twice

Question

1. Someone told me that technically one needs to pour water on each hand only once since we use large quantities of water. Is there a halachic source for this?

2. I heard that the requirement to pour twice over each hand (i.e. washing for bread), is really when you have only a revi’is of water (about three ounces) for both hands. Is there a halachic source for this?

Answer 1

The primary source for this is the Mishna - מסכת ידיים - Chapter 2 Mishna 1:

נָטַל לְיָדוֹ אַחַת מִשְּׁטִיפָה אַחַת, יָדוֹ טְהוֹרָה. לִשְׁתֵּי יָדָיו מִשְּׁטִיפָה אַחַת, רַבִּי מֵאִיר מְטַמֵּא, עַד שֶׁיִּטּוֹל מֵרְבִיעִית.