Allah, exalted be His praise, said concerning the person who is put to trial because of his religion and is able to emigrate but does not emigrate until he dies: "Indeed, those whose souls the angels take while they are wronging themselves - (the angels) say: In what condition were you? They say: We were weak (and oppressed) in the land." [Surah al-Nisa: 97] (the verse).
Hadith Referenceالسنن الكبرى للبيهقي / كتاب السير / Q17749
Muhammad bin Abd al-Rahman bin Nawfal al-Asadi said: The people of Madinah were ordered to send out an army, and my name too was written in it. (Meanwhile) I met Ikrimah, the freed slave of Ibn Abbas (may Allah be pleased with them both), and he forbade me most strongly, and said: Ibn Abbas (may Allah be pleased with them both) informed me that there were some people from among the Muslims who were with the army of the polytheists and caused their numbers to increase, and did not join the Messenger of Allah (peace and blessings be upon him). So whenever an arrow came from the Muslims' side it would strike them and they would die, or they would otherwise be killed. So Allah Almighty revealed this verse concerning them: "Indeed, those whose souls the angels take while they are wronging themselves - (the angels) ask them: In what condition were you (why did you not emigrate)? They answer: We were weak and oppressed in the land. The angels say: Was not the earth of Allah spacious enough for you to emigrate in it? For those, their refuge is Hell, and evil it is as a destination." [Surah al-Nisa: 97]
Hadith Referenceالسنن الكبرى للبيهقي / كتاب السير / 17749
Sayyiduna Jarir bin Abdullah al-Bajali (may Allah be pleased with him) says that the Messenger of Allah (peace and blessings be upon him) said: "Whoever stays with the polytheists, he is free of the protection of Allah."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب السير / 17750
Sayyiduna Jarir bin Abdullah (may Allah be pleased with him) says: I came to the Prophet (peace and blessings be upon him) while he was taking the pledge of allegiance from the people. I said: O Prophet of Allah! Stretch out your hand so that I may pledge allegiance to you, and also lay down for me whatever conditions you consider appropriate for me. So he (peace and blessings be upon him) said: "I take your pledge on condition that you worship Allah, establish the prayer, pay the zakah, sincerely wish well for the believer, and separate yourself from the polytheist."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب السير / 17751
Yazid bin Abdullah bin al-Shikhkhir (may Allah have mercy on him) says: Once we were in the camel enclosure (al-Mirbad) when a Bedouin with dishevelled hair came to us, carrying a piece of hide or of leather. We said: It seems this man is not from our town. He said: Yes, I am not from your town; I have a letter which the Messenger of Allah (peace and blessings be upon him) had written for me. The people said: Show it! So I took it from him and read it, and these words were written in it: "'Bismillah al-Rahman al-Rahim' (In the name of Allah, the Most Gracious, the Most Merciful). This letter is from Muhammad, the Messenger of Allah (peace and blessings be upon him), to Banu Zuhayr bin Uqaysh." Abu al-Ala (may Allah have mercy on him) said: They are a clan of the Ukl tribe. "If you bear witness to 'La ilaha illallah' (There is no god but Allah), establish the prayer, pay the zakah, separate yourselves from the polytheists, and pay one-fifth of the spoils of war, and the share of the Prophet (peace and blessings be upon him) and the safi (the portion chosen for him) - when you do this, you will be under the protection of Allah and the protection of His Messenger."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب السير / 17752