Allah said,

﴿وَأَنزْلْنَا الْحَدِيدَ فِيهِ بَأْسٌ شَدِيدٌ﴾

(And We brought forth iron wherein is mighty power,) meaning, `We made iron a deterrent for those who refuse the truth and oppose it after the proof has been established against them.' Allah's Messenger remained in Makkah for thirteen years. During that time, the revelation continued being sent to him, containing arguments against the idolators and explaining Tawhid with detail and proofs. When the evidence was established against those who defied the Messenger , Allah decreed the Hijrah. Then He ordered the believers to fight the disbelievers using swords, using them to strike the necks and foreheads of those who opposed, rejected and denied the Qur'an. Imam Ahmad and Abu Dawud recorded that `Abdullah bin `Umar said that the Messenger of Allah said,

«بُعِثْتُ بِالسَّيْفِ بَيْنَ يَدَيِ السَّاعَةِ حَتْى يُعْبَدَ اللهُ وَحْدَهُ لَا شَرِيكَ لَهُ، وَجُعِلَ رِزْقِي تَحْتَ ظِلِّ رُمْحِي، وَجُعِلَ الذِّلَّةُ والصَّغَارُ عَلَى مَنْ خَالَفَ أَمْرِي، وَمَنْ تَشَبَّهَ بِقَوْمٍ فَهُوَ مِنْهُم»

(I was sent with the sword just before the Hour so that Allah be worshipped alone without partners. My provision was placed under the shadow of my spear, and those who defy my order were disgraced and humiliated, and he who imitates a people is one of them.) This is why Allah the Exalted said,

﴿فِيهِ بَأْسٌ شَدِيدٌ﴾

(wherein is mighty power,) in reference to weapons, such as swords, spears, daggers, arrows, shields, and so forth,

﴿وَمَنَـفِعُ لِلنَّاسِ﴾

(as well as many benefits for mankind,) meaning, in their livelihood, such as using it to make coins, hammers, axes, saws chisels, shovels and various tools that people use for tilting the land, sowing, cooking, making dough and manufacturing other objects necessary for their livelihood. Allah's statement,

﴿وَلِيَعْلَمَ اللَّهُ مَن يَنصُرُهُ وَرُسُلَهُ بِالْغَيْبِ﴾

(that Allah may test who it is that will help Him (His religion) and His Messengers in the unseen.) meaning, whose intention by carrying weapons is the defense of Allah (His religion) and His Messenger,

﴿إِنَّ اللَّهَ قَوِىٌّ عَزِيزٌ﴾

(Verily, Allah is Powerful, Almighty.) meaning, surely, Allah is Powerful, Almighty, and He gives victory to those who give victory and aid to Him. However, Allah does not need mankind's help, but He ordered Jihad to test people with each other.

﴿وَلَقَدْ أَرْسَلْنَا نُوحاً وَإِبْرَهِيمَ وَجَعَلْنَا فِى ذُرِّيَّتِهِمَا النُّبُوَّةَ وَالْكِتَـبَ فَمِنْهُمْ مُّهْتَدٍ وَكَثِيرٌ مِّنْهُمْ فَـسِقُونَ - ثُمَّ قَفَّيْنَا عَلَى ءَاثَـرِهِم بِرُسُلِنَا وَقَفَّيْنَا بِعِيسَى ابْنِ مَرْيَمَ وَءَاتَيْنَـهُ الإِنجِيلَ وَجَعَلْنَا فِى قُلُوبِ الَّذِينَ اتَّبَعُوهُ رَأْفَةً وَرَحْمَةً وَرَهْبَانِيَّةً ابتَدَعُوهَا مَا كَتَبْنَـهَا عَلَيْهِمْ إِلاَّ ابْتِغَآءَ رِضْوَنِ اللَّهِ فَمَا رَعَوْهَا حَقَّ رِعَايَتِهَا فَـَاتَيْنَا الَّذِينَ ءَامَنُواْ مِنْهُمْ أَجْرَهُمْ وَكَثِيرٌ مِّنْهُمْ فَـسِقُونَ ﴾

(26. And indeed, We sent Nuh and Ibrahim, and placed in their offspring prophethood and Scripture. And among them there are some who are guided; but many of them are rebellious.) (27. Then, We sent after them Our Messengers, and We sent `Isa the son of Maryam, and gave him the Injil. And We ordained in the hearts of those who followed him, compassion and mercy. But the monasticism which they invented for themselves, We did not prescribe for them, but (they sought it) only to please Allah therewith, but that they did not observe it with the right observance. So, We gave those among them who believed, their (due) reward; but many of them are rebellious.)