וַיַּבֵּ֕ט וְהִנֵּ֧ה מְרַאֲשֹׁתָ֛יו עֻגַ֥ת רְצָפִ֖ים וְצַפַּ֣חַת מָ֑יִם וַיֹּ֣אכַל וַיֵּ֔שְׁתְּ וַיָּ֖שָׁב וַיִּשְׁכָּֽב׃
And he looked, and, behold, there was at his head a cake baked on the hot stones, and a cruse of water. And he did eat and drink, and laid him down again.
Rashi
a glowing coal Heb. רִצְפָּה, a coal, and similarly, (I Kings 19:6) “a cake baked on hot coals (עֻגַּת רְצָפִים),” like עֻגַּת רְשָׁפִים. In regards to Isaiah and Elijah, however, it is written with a ‘zadi,’ רִצְפָּה, because they spoke ill of Israel. This one [Isaiah] called them a people of unclean lips, and this one [Elijah] said, (ibid. 10) “For...have forsaken Your covenant.” Said the Holy One, blessed be He, to the angel, “Break the mouth (רְצוֹץ פֶּה) that spoke ill of My children.”