Sayyiduna Ubadah bin Samit (may Allah be pleased with him) and Sayyiduna Shaddad bin Aws (may Allah be pleased with him), both of these companions narrate: "There are two types of twilight (shafaq): the red one and the white one. When the red twilight disappears, then the time for prayer begins. Similarly, there are two types of true dawn (subh sadiq): one that is vertical and one that is horizontal. When the horizontal one ends, then the time for prayer begins."