I saw the Prophet ﷺ in a dream at midday, disheveled and dust-covered, carrying a flask containing blood, gathering something into it or tracing something out.I asked, "Messenger of Allah, what is this?"He replied, "This is the blood of Husayn and his companions. I have been gathering it all day."Ammar said, We took note of that day, and we found that he was killed on that very day.
حدثنا عبد الرحمن حدثنا حماد بن سلمة عن عمار بن أبي عمار
رأيت النبي ﷺ في المنام بنصف النهار أشعث أغبر معه قارورة فيها دم يلتقطه أو يتتبع فيها شيئا قال قلت يا رسول الله ما هذا قال دم الحسين وأصحابه لم أزل أتتبعه منذ اليوم قال عمار فحفظنا ذلك اليوم فوجدناه قتل ذلك اليوم
Its isnad is sahih. It is found in Majma al-Zawaid 9:193-194, where it is stated, "Ahmad and Tabarani reported it, and the narrators of Ahmad are the narrators of the Sahih." See also 648.