Umayr bin Sa'id said: We were sitting with Sayyiduna Ibn Mas'ud (may Allah be pleased with him), and Sayyiduna Abu Musa (may Allah be pleased with him) was also with him, when the governor seized a man, beat him and mounted him on a camel. The people began to say: The camel! The camel! (That is the sign.) A man said: O Abu Abd al-Rahman! This is the camel we used to hear about. Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) said: "Then where is the flash (of lightning)?"
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 10458