Rain- Gevurah

in the first blatt of mesachtas Tannis we want to prove that rain comes down with gevurah so we have a gezaira shova חֵקֶר-חֵקֶרr from Rain to brias haolam and then from brias haolam to gevurah My question is why go the long route of brias haolam to gevurah, we have in Ashrei everyday וְלִגְדֻלָּתוֹ אֵין חֵקֶר we have חֵקֶר there and in the next Pasuk we have gevura וּגְבוּרֹתֶיךָ יַגִּידוּ why dont we just use this?

Thank you for your question.

Since in the Ashrey it is not specifically speaking about rain, and we want to have a source that rain is Gevurah therefore we first establish that rain is like the creation of the world, then we learn that like the creation of the world, is called Gevurah same too rain.

Wishing you all the best, Hatsalcha Rabba.