Quran

Allah says that what befell them of killing and defeat on the day the two armies met, the Muslim army and the polytheist army at Uhud, was by His permission, and in accordance with His will and decree that cannot be avoided and must inevitably come to pass. When the divine decree comes to pass, there is no option but to submit to it and accept it, for there is a great wisdom behind His decree, it brings immense benefits, and it is ordained so that the believer would be distinguished from the hypocrite. Al-Saadi: 156.
Question: Muslims benefited from their defeat at Uhud. Explain.

(Obeyed us) by not going out against Quraysh. (They stayed behind) meaning: They said this statement and sat back themselves from Jihad . Allah responded to them: (Say, then avert death from yourselves) meaning: Say to them, O Muhammad, if you are truthful, then avert death from yourselves. The Arabic word (dar') means ward off. This shows that caution does not avail one against his fate. A person who is killed can only be killed according to his appointed time, and what Allah knows and says will inevitably happen. Al-Qurtubi: 5/405.
Question: Does Jihad have an impact on the timing of a person's death?

(Rather, they are alive) indicates that martyrs are alive and enjoying the provisions of Paradise, unlike the rest of the dead believers who do not enjoy these provisions until they enter Paradise on the Day of Resurrection. Ibn Juzay: 1/166.
Question: The martyrs are alive after being killed. Explain.

The phrase (with their Lord) is indicative of their high status and their closeness to their Lord (receiving provision) of various kinds of delights that cannot be known or described, except by the One Who bestowed it upon them. Moreover, they are (rejoicing in what Allah has bestowed upon them out of His bounty) that is, they are very happy with it, delighted with it and rejoicing in it. That is because it is beautiful, abundant and great, and there is immense joy when attaining it and there is nothing to spoil that joy. For them, Allah combined the physical joy of the provision and the spiritual joy, with the joy of that which He bestows upon them out of His bounty. Thus, their joy and happiness are complete. Al-Saadi: 156.
Question: Allah combines for the martyr the bliss of the body and the bliss of the heart and soul. Explain.

They lost nothing except the life of distress which no one desires, and they will gain the life of permanent bliss in which no tribulation, sorrow will befall them, nor dismay will touch them on the Day of Gathering. Al-Biqai: 2/180.
Question: What is the reward of those who are killed in the cause of Allah?

They receive good tidings about their brethren, whom they left behind in this life, following the paths of faith and Jihad that they will receive the same great reward when they are martyred. Therefore, the martyrs are rejoiced over this good tidings. Al-Baghawi: 1/448.
Question: Why do martyrs receive good tidings about their brethren?

(Allah is Sufficient for us, and He is the best Protector) these words are the believer's defense against what is feared and hated. These are the same words said by Abraham (u) when he was thrown into the fire. (Allah is Sufficient) He alone is sufficient for us, so we have no fear of anything except Him. (He is the best Protector) this is a praise of Allah and that He is the best refuge from all harms. (So they returned) they returned safe and rewarded. Ibn Juzay: 1/167.
Question: What is the meaning of (Allah is Sufficient for us, and He is the best Protector)?