It is narrated from Yusuf al-Makki (may Allah have mercy on him) that a companion of ours had a wet dream while he was wounded and had bandaged his chest. We asked Ubayd bin Umayr (may Allah have mercy on him), and he said: He should take a ritual bath and wipe over the cloth, or he said: wipe over his chest.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الطهارة / 1083