"You shall eat no fat and no blood" (Leviticus 3:17). Rabbi Yehuda says: it likens blood to fat - just as fat falls under two prohibitions, and so forth. And the Sages say: there is in it only a single warning. One might think that for the blood of consecrated animals that became unfit one would be liable under two prohibitions; therefore Scripture says, "Only the blood you shall not eat" (Deuteronomy 12:16) - there is in it only a single warning. I have only their blood; from where their fat? Scripture says "fat and blood" - it likens fat to blood: just as blood is under one prohibition, so too fat is under one prohibition. For since the firstborn went out from the category of consecrated animals that became unfit, one might think one would be liable for its blood under two prohibitions; therefore Scripture says, "Only its blood you shall not eat" (Deuteronomy 15:23) - there is in it only a single warning. I have only its blood; from where its fat? Scripture says "fat and blood" - just as blood is under one prohibition, so too fat is under one prohibition.
You Shall Eat No Fat and No Blood
Yalkut Shimoni on Torah 464:1
כָּל חֵלֶב וְכָל דָּם לֹא תֹאכֵלוּ, רַבִּי יְהוּדָה אוֹמֵר מַקִּישׁ דָּם לְחֵלֶב מַה חֵלֶב בִּשְׁנֵי לָאוִין וְכוּ' וַחֲכָמִים אוֹמְרִים אֵין בּוֹ אֶלָּא אַזְהָרָה אַחַת יָכוֹל אַף דַּם פְּסוּלֵי הַמֻּקְדָּשִׁים יְהוּ חַיָּבִין עָלָיו בִּשְׁנֵי לָאוִין תַּלְמוּד לוֹמַר "רַק הַדָּם לֹא תֹאכֵלוּ", אֵין בּוֹ אֶלָּא אַזְהָרָה אַחַת אֵין לִי אֶלָּא דָּמָם, חֶלְבָּם מִנַּיִן תַּלְמוּד לוֹמַר "חֵלֶב וְדָם", הִקִּישׁ חֵלֶב לְדָם מַה דָּם בְּלָאו אֶחָד אַף חֵלֶב בְּלָאו אֶחָד, שֶׁמִּתּוֹךְ שֶׁיָּצָא הַבְּכוֹר מִכְּלַל פְּסוּלֵי הַמֻּקְדָּשִׁים יָכוֹל יְהוּ חַיָּבִין עַל דָּמוֹ שְׁנֵי לָאוִין תַּלְמוּד לוֹמַר (שם טו, כג) "רַק אֶת דָּמוֹ לֹא תֹאכֵל", אֵין בּוֹ אֶלָּא אַזְהָרָה אַחַת אֵין לִי אֶלָּא דָּמוֹ חֶלְבּוֹ מִנַּיִן תַּלְמוּד לוֹמַר "חֵלֶב וְדָם", מַה דָּם בְּלָאו אֶחָד אַף חֵלֶב בְּלָאו אֶחָד.