Allah Most High ordered the believers to fight the Disbelievers [Kuffar] first, and the nearest ones first, that is, those nearest to the land of Islam. For this reason the Messenger of Allah (SAW) began by fighting the Idolaters [Mushrikun] in the Arabian peninsula. When He finished with them, and Allah gave him victory over Mecca, Medina, Ta’if, Yemen, Al-yamama, Hajr, Khaybar, Hadramawt, and other territories of the Arabian peninsula, and people from among the rest of the Arabs entered into the religion [deen] of Allah in droves, He set out to fight the People of the Book. He got ready to raid the Romans, the people nearest to the Arabian peninsula, and the first people to be called to Islam, since they were a people of the book. He reached Tabuk but then turned back due to the weariness of the people, drought in the land, and tight circumstances. This was in the ninth year after his (peace be upon him) emigration [hijra].
Then in the tenth year He became occupied with his pilgrimage, the farewell pilgrimage; then the end came upon him (may the prayers and peace of Allah be upon him) eighty-one days after the pilgrimage; Allah preferred for him to be with what He had for him. And after him, his adviser, friend, and caliph Abu Bakr (may Allah be pleased with him) took command. And the deen fell under attack and was almost dissipated, except that Allah Most High affirmed it by him, and he fortified the foundations and affirmed the supports. He brought back, being compelled to, those who wandered from the deen, and brought back to Islam those who had apostatized. He took zakat from those abject people who had banned it, and manifested the truth to those who were unaware of it. And he carried out for the Messenger what He had imparted to him. Then he set out to prepare the Islamic armies against the Romans, the cross worshippers, and the Persians, the fire worshippers. And Allah by a blessing gave him victory over the land in his mission, and brought down Khosrow and Caesar, as well as those people who obeyed the two of them. And he spent their treasures in the cause of Allah, as the Messenger of God had told.
The matter was brought to completion at the hands of his successor after him, the one who followed his time in power, Al-Faruq the Ever-repentant, martyred in the prayer niche, Abu Hafs ‘Umar ibn Al-Khattab. Allah disgraced the heretical Disbelievers, quashed the tyrants and the hypocrites, and appropriated kingdoms east and west. And the storehouses of riches from the rest of the territories, near and far, were brought to him, and he divided them up lawfully and agreeably.
Then when he died a martyr, having lived a praiseworthy life, the Companions from among the Emigrants [muhajirun] and the Ansar agreed to the caliphate of the Leader of the Faithful Abu ‘Amr ‘Uthman ibn ‘Affan, martyr of the abode. And by his majesty he clothed Islam amply with authority, and the remaining territories were furnished, over peoples' necks, with the full proof of Allah. And Islam was manifest in the eastern and western regions of the earth; and the word of Allah was raised up and his deen made manifest. And the true ummah attained the utmost of its aims from the enemies of Allah; every time they surpassed a nation, they moved on to whoever was next, and then to the wantonly haughty who were close to them, following the word of the Most High: { Oh you who have believed, fight the Disbelievers who are near to you } and the word of the Most High: { And may they find harshness in you } ; that is, may the Disbelievers find harshness from you in your fighting them. Indeed the full Believer is he who is a companion to his believing brother but harsh to his disbelieving enemy.