إِذَا خَافَ الصُّبْحَ فَلَا بَأْسَ بِهِ.
Hadith.122 - Ali ibn Ja'far asked his brother Imam Musa ibn Jafar Al-Kadhim (as) bout a man who uses his hand to clean his teeth when he gets up for the night prayer (Salat Al Layl), even though he has access to siwak. Imam (as) said: "If he fears that dawn is approaching, there is no harm in doing so."