Reference for Berakhot 29:4

א"ל שפיר קאמר מי כתיב ארחץ במים בנקיון כתיב כל מידי דמנקי דהא רב חסדא לייט אמאן דמהדר אמיא בעידן צלותא

He answered : Well has he spoken ; for is it written, "I will wash with water"? No; it is written, "I will wash in cleanliness," i.e. with anything that cleanses. And lo, Rab Hisda cursed anyone who went about in search of water at the time of prayer. This, however, applies only to the reading of the Shema', but for the Tefillah one may go for water.

Jastrow