إِنَّا لِلَّهِ وَإِنَّا إِلَيْهِ رَاجِعُونَ
Inna lillahi wa inna ilayhi raji'un
Indeed, to Allah we belong and to Him we shall return.
The istirja' — said upon hearing any bad news, any loss, any calamity. The Quran says those who say this when struck by misfortune "are the ones upon whom are blessings from their Lord and mercy. And it is those who are the rightly guided" (2:157). Two facts that reframe every tragedy: you belong to Allah (so He has the right to take what is His), and you are returning to Him (so this separation is temporary).
Related Du'as
اللَّهُمَّ لَا سَهْلَ إِلَّا مَا جَعَلْتَهُ سَهْلًا وَأَنْتَ تَجْعَلُ الْحَزْنَ إِذَا شِئْتَ سَهْلًا
O Allah, nothing is easy except what You make easy, and You can make difficulty easy if You wish.
Sahihاللَّهُ اللَّهُ رَبِّي لَا أُشْرِكُ بِهِ شَيْئًا
Allah, Allah is my Lord. I do not associate anything with Him.
Hasanلَا إِلَٰهَ إِلَّا أَنتَ سُبْحَانَكَ إِنِّي كُنتُ مِنَ الظَّالِمِينَ
There is no deity except You; exalted are You. Indeed, I have been of the wrongdoers.
Sahihاللَّهُمَّ اجْعَلْ لِي مِنْ كُلِّ هَمٍّ فَرَجًا وَمِنْ كُلِّ ضِيقٍ مَخْرَجًا وَارْزُقْنِي مِنْ حَيْثُ لَا أَحْتَسِبُ
O Allah, grant me relief from every worry, a way out from every difficulty, and provide for me from where I do not expect.
Hasan