Musnad Ahmad Hadith 17693

It is narrated from Abdullah bin Busr (may Allah be pleased with him) that the Messenger of Allah (ﷺ) said: "On the Day of Resurrection, I will recognize each of my followers." The companions (may Allah be pleased with them) asked, "O Messenger of Allah! (ﷺ) In such a large crowd of creation, how will you recognize them?" The Prophet (ﷺ) said, "Tell me, if you enter a stable where black horses are tied and among them there is a horse whose forehead is bright, shining, and white, would you be able to recognize it among those horses?" They replied, "Why not?" The Prophet (ﷺ) said, "In the same way, on that day, the foreheads of my followers will be radiant due to prostration, and their limbs will be shining because of ablution."