Allah said,
﴿الَّذِينَ اسْتَجَابُواْ لِلَّهِ وَالرَّسُولِ مِن بَعْدِ مَآ أَصَـبَهُمُ الْقَرْحُ﴾
(Those who answered (the Call of) Allah and the Messenger after being wounded) ﴿3:172﴾.
This occurred on the day of Hamra' Al-Asad. After the idolators defeated the Muslims (at Uhud), they started on their way back home, but soon they were concerned because they did not finish off the Muslims in Al-Madinah, so they set out to make that battle the final one. When the Messenger of Allah got news of this, he commanded the Muslims to march to meet the disbelievers, to bring fear to their hearts and to demonstrate that the Muslims still had strength to fight. The Prophet only allowed those who were present during Uhud to accompany him, except for Jabir bin `Abdullah Al-Ansari, as we will mention. The Muslims mobilized, even though they were still suffering from their injuries, in obedience to Allah and His Messenger .
Ibn Abi Hatim recorded that `Ikrimah said, "When the idolators returned ﴿towards Makkah﴾ after Uhud, they said, `You neither killed Muhammad nor collected female captives. Woe to you for what you did. Let us go back.' When the Messenger of Allah heard this news, he mobilized the Muslim forces, and they marched until they reached Hamra Al-Asad. The idolators said, `Rather, we will meet next year', and the Messenger of Allah went back ﴿to Al-Madinah﴾, and this was considered a Ghazwah (battle). Allah sent down,
﴿الَّذِينَ اسْتَجَابُواْ لِلَّهِ وَالرَّسُولِ مِن بَعْدِ مَآ أَصَـبَهُمُ الْقَرْحُ لِلَّذِينَ أَحْسَنُواْ مِنْهُمْ وَاتَّقَوْاْ أَجْرٌ عَظِيمٌ ﴾
(Those who answered (the Call of) Allah and the Messenger after being wounded; for those of them who did good deeds and feared Allah, there is a great reward.)
Al-Bukhari recorded that `A'ishah said to `Urwah about the Ayah;
﴿الَّذِينَ اسْتَجَابُواْ لِلَّهِ وَالرَّسُولِ﴾
(Those who answered (the Call of) Allah and the Messenger)
"My nephew! Your fathers Az-Zubayr and Abu Bakr were among them. After the Prophet suffered the calamity at Uhud and the idolators went back, he feared that the idolators might try to come back and he said, `Who would follow them' Seventy men, including Az-Zubayr and Abu Bakr, volunteered.'' This was recorded by Al-Bukhari alone.
As for Allah's statement,
﴿الَّذِينَ قَالَ لَهُمُ النَّاسُ إِنَّ النَّاسَ قَدْ جَمَعُواْ لَكُمْ فَاخْشَوْهُمْ فَزَادَهُمْ إِيمَـناً﴾
(Those unto whom the people said, "Verily, the people have gathered against you, therefore, fear them.'' But it (only) increased them in faith) ﴿3:173﴾, it means, those who threatened the people, saying that the disbelievers have amassed against them, in order to instill fear in them, but this did not worry them, rather, they trusted in Allah and sought His help,
﴿وَقَالُواْ حَسْبُنَا اللَّهُ وَنِعْمَ الْوَكِيلُ﴾
(and they said: "Allah is Sufficient for us, and He is the Best Disposer of affairs.'')
Al-Bukhari recorded that Ibn `Abbas said,
﴿حَسْبُنَا اللَّهُ وَنِعْمَ الْوَكِيلُ﴾
("Allah Alone is Sufficient for us and He is the Best Disposer of affairs for us.'')
"Ibrahim said it when he was thrown in fire. Muhammad said it when the people said, `Verily, the people have gathered against you, therefore, fear them.' But it only increased them in faith, and they said, `Allah is Sufficient for us and He is the Best Disposer of affairs for us.''' Abu Bakr Ibn Marduwyah recorded that Anas bin Malik said that the Prophet was told on the day of Uhud, "Verily, the people have gathered against you, therefore, fear them.'' Thereafter, Allah sent down this Ayah ﴿3:173﴾.
This is why Allah said,
﴿فَانْقَلَبُواْ بِنِعْمَةٍ مِّنَ اللَّهِ وَفَضْلٍ لَّمْ يَمْسَسْهُمْ سُوءٌ﴾
(So they returned with grace and bounty from Allah. No harm touched them;) for when they relied on Allah, Allah took care of their worries, He confounded the plots of their enemies, and the Muslims returned to their land,
﴿بِنِعْمَةٍ مِّنَ اللَّهِ وَفَضْلٍ لَّمْ يَمْسَسْهُمْ سُوءٌ﴾
(with grace and bounty from Allah. No harm touched them;) safe from the wicked plots of their enemies,
﴿وَاتَّبَعُواْ رِضْوَنَ اللَّهِ وَاللَّهُ ذُو فَضْلٍ عَظِيمٍ﴾
(and they followed the pleasure of Allah. And Allah is the Owner of great bounty.)
Al-Bayhaqi recorded that Ibn `Abbas said about Allah's statement,
﴿فَانْقَلَبُواْ بِنِعْمَةٍ مِّنَ اللَّهِ وَفَضْلٍ﴾
(So they returned with grace and bounty from Allah,) "The `Grace' was that they were saved. The `Bounty' was that a caravan passed by, and those days were ﴿Hajj﴾ season days. Thus the Messenger of Allah bought and sold and made a profit, which he divided between his Companions.''
Allah then said,
﴿إِنَّمَا ذَلِكُمُ الشَّيْطَـنُ يُخَوِّفُ أَوْلِيَاءَهُ﴾
(It is only Shaytan that suggests to you the fear of his friends,) ﴿3:175﴾ meaning, Shaytan threatens you with his friends and tries to pretend they are powerful and fearsome. Allah said next,
﴿فَلاَ تَخَافُوهُمْ وَخَافُونِ إِن كُنتُمْ مُّؤْمِنِينَ﴾
(so fear them not, but fear Me, if you are indeed believers.) meaning, "If Shaytan brings these thoughts to you, then depend on Me and seek refuge with Me. Indeed, I shall suffice you and make you prevail over them.'' Similarly, Allah said,
﴿أَلَيْسَ اللَّهُ بِكَافٍ عَبْدَهُ وَيُخَوِّفُونَكَ بِالَّذِينَ مِن دُونِهِ﴾
(Is not Allah Sufficient for His servant Yet they try to frighten you with those besides Him!) ﴿39: 36﴾, until,
﴿قُلْ حَسْبِىَ اللَّهُ عَلَيْهِ يَتَوَكَّـلُ الْمُتَوَكِّلُونَ﴾
(Say: "Sufficient for me is Allah; in Him those who trust must put their trust.'') ﴿39:38﴾. Allah said,
﴿فَقَـتِلُواْ أَوْلِيَاءَ الشَّيْطَـنِ إِنَّ كَيْدَ الشَّيْطَـنِ كَانَ ضَعِيفاً﴾
(So fight you against the friends of Shaytan; ever feeble indeed is the plot of Shaytan.) ﴿4:76﴾ and
﴿أُوْلَـئِكَ حِزْبُ الشَّيْطَـنِ أَلاَ إِنَّ حِزْبَ الشَّيْطَـنِ هُمُ الخَـسِرُونَ﴾
(They are the party of Shaytan. Verily, it is the party of Shaytan that will be the losers!) ﴿58:19﴾,
﴿كَتَبَ اللَّهُ لاّغْلِبَنَّ أَنَاْ وَرُسُلِى إِنَّ اللَّهَ قَوِىٌّ عَزِيزٌ ﴾
(Allah has decreed: "Verily, it is I and My Messengers who shall be the victorious.'' Verily, Allah is All-Powerful, All-Mighty.) ﴿58:21﴾ and
﴿وَلَيَنصُرَنَّ اللَّهُ مَن يَنصُرُهُ﴾
(Verily, Allah will help those who help His (cause).) ﴿22:40﴾ and
﴿يأَيُّهَا الَّذِينَ ءَامَنُواْ إِن تَنصُرُواْ اللَّهَ يَنصُرْكُمْ﴾
(O you who believe! If you help (in the cause of) Allah, He will help you) ﴿47:7﴾, and,
﴿إِنَّا لَنَنصُرُ رُسُلَنَا وَالَّذِينَ ءَامَنُواْ فِى الْحَيَوةِ الدُّنْيَا وَيَوْمَ يَقُومُ الاٌّشْهَـدُ - يَوْمَ لاَ يَنفَعُ الظَّـلِمِينَ مَعْذِرَتُهُمْ وَلَهُمُ الْلَّعْنَةُ وَلَهُمْ سُوءُ الدَّارِ ﴾
(Verily, We will indeed make victorious Our Messengers and those who believe, in this world's life and on the Day when the witnesses will stand forth. The Day when their excuses will be of no profit to wrongdoers. Theirs will be the curse, and theirs will be the evil abode.) ﴿40:51,52﴾
﴿وَلاَ يَحْزُنكَ الَّذِينَ يُسَـرِعُونَ فِى الْكُفْرِ إِنَّهُمْ لَن يَضُرُّواْ اللَّهَ شَيْئاً يُرِيدُ اللَّهُ أَلاَّ يَجْعَلَ لَهُمْ حَظّاً فِى الاٌّخِرَةِ وَلَهُمْ عَذَابٌ عَظِيمٌ - إِنَّ الَّذِينَ اشْتَرَوُاْ الْكُفْرَ بِالإِيمَـنِ لَن يَضُرُّواْ اللَّهَ شَيْئاً وَلهُمْ عَذَابٌ أَلِيمٌ - وَلاَ يَحْسَبَنَّ الَّذِينَ كَفَرُواْ أَنَّمَا نُمْلِى لَهُمْ خَيْرٌ لاًّنفُسِهِمْ إِنَّمَا نُمْلِى لَهُمْ لِيَزْدَادُواْ إِثْمَاً وَلَهْمُ عَذَابٌ مُّهِينٌ ﴾
﴿مَّا كَانَ اللَّهُ لِيَذَرَ الْمُؤْمِنِينَ عَلَى مَآ أَنتُمْ عَلَيْهِ حَتَّى يَمِيزَ الْخَبِيثَ مِنَ الطَّيِّبِ وَمَا كَانَ اللَّهُ لِيُطْلِعَكُمْ عَلَى الْغَيْبِ وَلَكِنَّ اللَّهَ يَجْتَبِى مِن رُّسُلِهِ مَن يَشَآءُ فَـَامِنُواْ بِاللَّهِ وَرُسُلِهِ وَإِن تُؤْمِنُواْ وَتَتَّقُواْ فَلَكُمْ أَجْرٌ عَظِيمٌ - وَلاَ يَحْسَبَنَّ الَّذِينَ يَبْخَلُونَ بِمَآ ءَاتَـهُمُ اللَّهُ مِن فَضْلِهِ هُوَ خَيْراً لَّهُمْ بَلْ هُوَ شَرٌّ لَّهُمْ سَيُطَوَّقُونَ مَا بَخِلُواْ بِهِ يَوْمَ الْقِيَـمَةِ وَللَّهِ مِيرَاثُ السَّمَـوَتِ وَالاٌّرْضِ وَاللَّهُ بِمَا تَعْمَلُونَ خَبِيرٌ ﴾
(176. And let not those grieve you who rush with haste to disbelieve; verily, not the least harm will they do to Allah. It is Allah's will to give them no portion in the Hereafter. For them there is a great torment.) (177. Verily, those who purchase disbelief at the price of faith, not the least harm will they do to Allah. For them, there is a painful torment.) (178. And let not the disbelievers think that Our postponing their punishment is good for them. We postpone the punishment only so that they may increase in sinfulness. And for them is a disgraceful torment.) (179. Allah will not leave the believers in the state in which you are now, until He distinguishes the wicked from the good. Nor will Allah disclose to you the secrets of the Unseen, but Allah chooses of His Messengers whom He wills. So believe in Allah and His Messengers. And if you believe and have Taqwa of Allah, then for you there is a great reward.) (180. And let not those who are stingy with that which Allah has bestowed on them of His bounty think that it is good for them. Nay, it will be worse for them; the things that they were stingy with shall be tied to their necks like a collar on the Day of Resurrection. And Allah's is the inheritance of the heavens and the earth; and Allah is Well-Acquainted with all that you do.)