It is narrated from 'Ubadah bin As-Samit, who said:
"[I asked] the Messenger of Allah (s.a.w) about For them are glad tidings in the life of the present world. He said: 'This refers to the righteous dreams which the Muslim sees or which are seen about him.'" (ES)
English reference (ES): Vol. 4, Book 8, Hadith 2275 (ES)
Arabic reference (ES): Book 34, Hadith 2444 (ES)