Tosefta for Berakhot 5:2
מַזְכִּירִין גְּבוּרוֹת גְּשָׁמִים בִּתְחִיַּת הַמֵּתִים, וְשׁוֹאֲלִין הַגְּשָׁמִים בְּבִרְכַּת הַשָּׁנִים, וְהַבְדָּלָה בְּחוֹנֵן הַדָּעַת. רַבִּי עֲקִיבָא אוֹמֵר, אוֹמְרָהּ בְּרָכָה רְבִיעִית בִּפְנֵי עַצְמָהּ. רַבִּי אֱלִיעֶזֶר אוֹמֵר, בְּהוֹדָאָה:
Gevuroth geshamim ("the mightiness of rain") is mentioned in techiyath hamethim (the resurrection prayer) [Gevuroth geshamim: "Mashiv haruach," which is not an expression of imploration, but of remembrance and praise. It is called "gevuroth geshamim" because rain is one of the mighty acts of the Holy One Blessed be He, viz. (Job 9:10): "He does great things, beyond searching out"; (Ibid. 5:10): "He gives rain upon the face of the earth."]; and rain is requested ["veten tal umatar livracha," (which is a request)] in birchath hashanim (the blessing of the years). [Because rain is sustenance, they placed the request for rain in the blessing of sustenance.]; and havdalah [at the conclusion of the Sabbath] is recited in chonen hada'ath ("who bestows knowledge") [which is the first weekday blessing. And, in the Yerushalmi: "Why was havdalah placed in chonen hada'ath? For without knowledge there is no havdalah ('discrimination')." And this is the halachah.] R. Akiva says: It is recited individually as the fourth blessing. R. Eliezer says: It is recited in the thanksgiving benediction.