Abdullah bin Malik al-Jayshani relates that he heard Sayyiduna Abu Basrah al-Ghifari (may Allah be pleased with him) say: The Messenger of Allah (peace and blessings be upon him) led us in the Asr prayer at al-Mukhammas, which is one of their valleys, then he said: "This prayer was presented to those before you, but they abandoned it. Indeed, whoever prays it will be given double the reward, and there is no prayer after it until you see the shahid (witness)." And by the shahid is meant the star.
Hadith Referenceالمعجم الكبير للطبراني / باب الجيم / 2153