Sayyiduna Sa'd bin Junadah (may Allah be pleased with him) says: I was present with the Prophet (peace and blessings be upon him) at "Hanif", and I heard him (peace and blessings be upon him) say: "Whoever gets up at night, performs ablution, rinses his mouth and then recites 'Subhanallah' one hundred times, 'Alhamdulillah' one hundred times and 'La ilaha illallah' one hundred times, his sins are forgiven, except for (matters of) bloodshed and property, for these are not annulled."
This narration was recorded by Imam al-Tabarani in al-Mu'jam al-Kabir; its chain contains a narrator, al-Husayn bin al-Hasan bin Atiyyah al-Awfi, who is "da'if" (weak).