Babylonian Talmud, Berakhot, Perek IX, Daf 56, Amud b:
"One who sees a shofar in a dream should rise early and recite 'And it shall come to pass in that day, that a great horn shall be blown;
and they shall come that were lost in the land of Assyria, and they
that were dispersed in the land of Egypt; and they shall worship the
LORD in the holy mountain at Jerusalem.' (Isaiah 27:13), before a different verse, in which shofar is a symbol of war, can precede it in becoming a reality: 'Blow you the shofar in Giva.'" (Hosea 5:8)
paraphrased from Adin Steinsaltz translation.