Sayyiduna Abu Hasan al-Ansari (may Allah be pleased with him), who was a Companion who took part in Badr and in al-Aqabah, said: We were sitting with the Messenger of Allah (peace and blessings be upon him) when a man stood up and forgot his sandals. Another man picked them up and put them under himself. When the man came back, he said: Where are my sandals? The people said: We have not seen them. Then a man said: Here they are. So the Messenger of Allah (peace and blessings be upon him) said: "What then of frightening a believer?" He said: O Messenger of Allah, I only did it in jest. He (peace and blessings be upon him) said: "What then of frightening a believer?" He repeated this two or three times.
Hadith Referenceالمعجم الكبير للطبراني / مسند من يعرف بالكنى / 19183