Oneness of Allah (Tawheed)

The believer who affirms the Oneness of Allaah (Tawheed) knows that everything happens by the decree of Allaah; what Allaah wills happens and what He does not will does not happen; there is nothing that can block the will of Allaah from being executed in His creation. Thus the heart of the believer who affirms the Oneness of Allaah is at rest, and he knows that there is no room for regret or grief in his life, because the command of Allaah preceded (the event) and His will is executed. Allaah says:

•►“No calamity befalls on the earth or in yourselves but it is inscribed in the Book of Decrees (Al‑Lawh Al‑Mahfooz) before We bring it into existence. Verily, that is easy for Allaah." [al-Hadeed 57:22]

•►“We will try you with fear and hunger, and loss of wealth and lives, and fruits; but give glad tidings to those who are patient. Who, when a misfortune overtakes them, say:
نﻮﻌﺟار ﻪﻴﻟإ ﺎﻧإو ﻪﻠﻟ ﺎﻧإ
`To Allah we belong and to Him we shall return.’ It is these on whom descend blessings and mercy from their Lord, and it is they who are rightly guided.” [Surah al-Baqarah: 155-157]

The Messenger of Allaah (SallAllahu alyhi Wasallam) said:
•►“There is no Muslim who is afflicted by a calamity and when he remembers it, even if it was in the dim and distant past, he says:
نﻮﻌﺟار ﻪﻴﻟإ ﺎﻧإو ﻪﻠﻟ ﺎﻧإ
inna lillāhi wa inna ilayhi rāji‘ūn (verily to Allāh we belong and unto Him is our return), but Allāh will give him a reward like that of the day when it befell him.”

[Muslim, Sahih, Book on funerals, no. 918; Abu Dawud, Sunan, Book on funerals, no. 3119; Ahmad ibn Hanbal, Musnad, vol. 6, p. 309; and Malik, Al-Muwatta', Book on funerals, no. 558.]