Can it be said of the deceased that he is in the care of Allah?
Question

What is the ruling on saying “So-and-so is in the care of Allah (fi dhimmatillah)” regarding one who has died?
Praise be to Allah.The Arabic word dhimmah (translated above as “care”) refers to a promise and guarantee to take care of someone or something.
Ibn al-Athir (may Allah have mercy on him) said: The words dhimmah and dhimam are often mentioned in the hadiths; they both refer to a covenant, safety, guarantee (of well-being), protection and entitlement…
One example is the hadith “He is no longer under the dhimmah (care) of Allah”, meaning that everyone has a promise that Allah will grant him well-being and take care of him, but if he exposes himself to unnecessary risk that will lead to his doom, or he does that which is forbidden to him, or he goes against what is enjoined upon him, he will no longer be under the protection and care of Allah, may He be exalted."( An-Nihayah fi Gharib al-Hadith  p. 455).
One of the hadiths in which dhimmatullah (the care of Allah) is mentioned is that in which the Prophet (blessings and peace of Allah be upon him) said: “Whoever prays Fajr is under the care of Allah, so do not fall short with regard to the rights of Allah, for anyone who does that, Allah will seize him and will throw him on his face into the Fire of Hell.” Narrated by Muslim (657).
An-Nawawi said in Sharh Muslim (5/158): Dhimmah here means protection or, it was said, safety. End quote.
See also the answer to question no. 72559 .
Based on this meaning, there is nothing wrong with saying of one who has died that he is in the care of Allah, meaning that he is under His protection. This is like a supplication asking Allah to protect him. It is like saying “He has moved to the mercy of Allah”; this is a supplication for him, asking that he be granted mercy. It is not a definitive statement that Allah has bestowed mercy upon him, because there is no way to know that.
Shaykh Ibn ‘Uthaymin (may Allah have mercy on him) was asked about saying “Fulan al-marhoom [So-and-so upon to whom divine mercy is shown]” or “May Allah envelop him in His mercy” or “He has moved to the mercy of Allah.”
He replied:
There is nothing wrong with saying “Fulan al-marhoom [So-and-so upon to whom divine mercy is shown]” or “May Allah envelop him in His mercy”, because saying these things is by way of optimism and hope; it is not a statement of fact. If it is said by way of optimism and hope, there is nothing wrong with it.
As for saying “He has moved to the mercy of Allah,” it seems to me that it also comes under the heading of optimism, and is not a statement of fact, because matters such as this are matters of the unseen, and we cannot be certain about them."(Majmu‘ Fatawa ash-Shaykh Ibn ‘Uthaymin  3/85).
It says in the hadith that was narrated from the Prophet (blessings and peace of Allah be upon him) that the deceased believer is in dhimmatillah (the care of Allah).
Abu Dawud (3202) narrated that Wathilah ibn al-Asqa‘ said: The Messenger of Allah (blessings and peace of Allah be upon him) led us in offering the funeral prayer for a Muslim man, and I heard him say: “O Allah, So and so the son of So and so is under Your care and Your protection, so protect him from the trial of the grave and the torment of Hellfire, for You are faithful to Your promise and You are praiseworthy. O Allah, forgive him and have mercy on him, for You are the Most Forgiving, Most Merciful.” Classed as sahih by al-Albani in Ahkam al-Jana’iz.
As-Sindi said in his commentary on Ibn Majah:
The words “under Your care (dhimmah)” mean: in safety, under Your covenant and protection.
Regarding the words “and Your care”, it was said: it was the custom of the Arabs to scare one another. If a man wanted to travel, he would seek a promise of protection from the leader of every tribe, so that he would be safe so long as he was in their territory, until he moved to the land of another tribe, where he would seek similar protection. This is what is meant, namely a promise of protection and safety so long as he was still in that leader’s land. End quote.
Al-Qari said in Mirqat al-Mafatih (3/1209):
“So and so the son of So and so is under Your care” means: He is under Your protection, because he believed in You. End quote.
Conclusion: There is nothing wrong with saying of a believer who has died that he is under the care of Allah, although this protection is not unique to the deceased, as we have noted from the hadith quoted above that the one who prays Fajr is under the care of Allah.
And Allah knows best.