Parashas Shemos · Side page (no TT primary unit)
וְהָיָ֡ה אִם־לֹ֣א יַאֲמִ֡ינוּ גַּם֩ לִשְׁנֵ֨י הָאֹת֜וֹת הָאֵ֗לֶּה וְלֹ֤א יִשְׁמְעוּן֙ לְקֹלֶ֔ךָ וְלָקַחְתָּ֙ מִמֵּימֵ֣י הַיְאֹ֔ר וְשָׁפַכְתָּ֖ הַיַּבָּשָׁ֑ה וְהָי֤וּ הַמַּ֙יִם֙ אֲשֶׁ֣ר תִּקַּ֣ח מִן־הַיְאֹ֔ר וְהָי֥וּ לְדָ֖ם בַּיַּבָּֽשֶׁת׃
And if they are not convinced by both these signs and still do not heed you, take some water from the Nile and pour it on the dry ground, and it—the water that you take from the Nile—will turn to blood on the dry ground.”
Shemos Rabbah 3:13 — EXTRA.
והיו לדם —\ldots סימן למכת הדם שתהא תחילה.
English: “And they shall become blood” — \ldots a sign of the plague of blood that would be first.
Custom
Chazal present the water-to-blood sign as the preview of the opening plague.