Abd al-Rahman bin Yazid narrated: We were with Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him), and when he said the salam (ending the prayer), he said: "By the One besides whom there is no god! This is the time of the sun's decline (duluk), and at this very time the time of this prayer has begun."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 9101