Sayyiduna Abdullah bin Malik bin Buhaynah (may Allah be pleased with him) narrates from his father Sayyiduna Malik bin Buhaynah (may Allah be pleased with him); he said: The Messenger of Allah (peace and blessings be upon him) passed by a man who was praying although the prayer had already been called (iqamah), and he (peace and blessings be upon him) said something to him which I do not know. When we finished the prayer, we gathered around him and asked: What did the Messenger of Allah (peace and blessings be upon him) say to you? He said: He (peace and blessings be upon him) said: "Soon people will be praying the Fajr prayer as four rak'ahs."
Hadith Referenceالمعجم الكبير للطبراني / باب الميم / 16712