Verse - The Noble Quran: Sourat 2, Verse 156.

In the Name of Allah, the Most Gracious, the Most Merciful.

156. Who, when afflicted with calamity, say: "Truly To Allah we belong and truly, to Him we shall return."

Comments:

[Inna lillahi wa inna ilayhi raji’oun] (Truly To Allah we belong and truly, to Him we shall return.) is the best quote to say when we are tested through what we like most, like when a beloved one is dead.  So, the Muslim witnesses that all that surrounds him belong to Allah, expresses his gratitude to him for the benefit he could take from them, does not get angry when Allah withdraw them from him, and also knows that all beloved ones will be retrieved on the Gathering Day.