Allah is the Most Merciful

On the authority of Abu Hurayrah (may Allah be pleased with him), who said that the Messenger of Allah (PBUH) said:

When Allah decreed the Creation He pledged Himself by writing in His book which is laid down with Him: My mercy prevails over my wrath. Meaning that Allah's merci always comes first and always overcomes his anger.

It was related by Muslim (also by al-Bukhari, an-Nasa'i and Ibn Majah).

Ibn Al-Mubarak Teaching

Ahmad ibn Abdullah al-Ajli said: My father told me he said: When Ibn al-Mubarak was dying, he made a man teach him to say: There is no god but Allah, and the man was insisting him. Then Ibn al-Mubarak said: you do not know how to do it, and I am afraid you could harm a Muslim after me, and he continued saying; if I say the word of Tawheed and do not speak after then let me, but if I say something else tell me to say it again until it becomes my last word.