About the Shofar and the Ram
The sons of Isaac are destined to sin before me and I will pass judgement on Rosh Hashana, unless they ask me to seek their credit, so they will blow the Shofar made from this ram’s horn, and I will remember the Binding of Isaac.
All that day, Avraham saw the ram clutching at this tree and he left and got out, clung to this forest, he clings to this thicket and waits and leaves. The Holy One, blessed be He, said to him, "Your children will cling to their sins and become entangled in the kingdoms from Babylon to Medai, from Medai to Greece, and from Greece to Edom." He asked: Good lord, this shall be so forever? HE said to him: and they will end up being redeemed by the horns of this ram. And on that day he blew a great shofar, and the lost ones from the land of Assyria and the expelled from the land of Egypt all came out and bow down to God on the holy mountain of Jerusalem.
Midrash Psikta of Cahana Rabbi