Reference for Bekhorot 10:9

מה נשתנו פטרי חמורים מפטרי סוסים וגמלים

R'Eliezer says: 'Rephidim' was the name [of a place], but R'Joshua says, it means that they relaxed [rifu] their hold on the words of the Law.

Jastrow

Jastrow

Jastrow