Bukhari

Hadith Commentary:
It is understood from this that, as far as possible, it is better to avoid fighting, if a good way of reconciliation can be found. Because Islam is strongly opposed to discord and corruption. However, when no other option remains and the enemy is determined to confront, then one must stand firm and face them resolutely, and at such a time, it is necessary to recite the prescribed supplication mentioned here. That is: "Allahumma munzil al-kitab, sari‘ al-hisab, ihzim al-ahzab, Allahumma ihzimhum wa zalzilhum wansurna ‘alayhim." Paradise is under the shade of swords.
This means that for Paradise, both financial and physical sacrifice is required; the bargain of Paradise is not a cheap bargain.
As mentioned in the verse of the Qur’an:
﴿إِنَّ اللَّهَ اشْتَرَىٰ مِنَ الْمُؤْمِنِينَ أَنفُسَهُمْ وَأَمْوَالَهُم بِأَنَّ لَهُمُ الْجَنَّةَ﴾ (, al-Tawbah: 111).

Hadith Commentary:
1.
The reason for waiting until the sun declines is that at this time the winds of assistance blow, and as the day cools, fighting is carried out with greater resolve. Moreover, Muslims pray for the mujahideen in their prayers. Thus, Nu'man bin Muqarrin radi Allahu anhu narrates:
He participated in a battle alongside the Messenger of Allah sallallahu alayhi wa sallam. When dawn broke, he would refrain from fighting; then, when the sun rose, he would fight until midday, then after the sun declined he would launch an attack, and at the time of 'Asr he would stop; then after the 'Asr prayer he would attack again.
It is said that at this time the winds of victory blow, and the believers pray for their armies in their prayers.
(Jami' al-Tirmidhi, al-Siyar, Hadith: 1612)
2.
By the wind of victory is meant the morning breeze (bad-e-saba), which generally becomes a cause of victory and assistance.
This hadith also shows that, in the view of Islam, war and fighting are not inherently desirable things.
As far as possible, avoidance of them has been encouraged.

Hadith Commentary:

That is, remain steadfast with perseverance, and no matter what the circumstances may be, never lose heart; cowardice or fleeing is not the characteristic of a believer. If death is not decreed, then surely you will return safely, and if death is decreed, then no power can save you. This is the very faith and conviction that bestows upon the believing man the honorable titles of "Ghazī" (victorious warrior) or "Shahīd" (martyr).

The command of Allah is:
﴿یٰٓاَیُّھَا الَّذِیْنَ اٰمَنُوا اسْتَعِیْنُوا بِالصَّبْرِ وَالصَّلٰوۃِ اِنَّ اللہَ مَعَ الصّٰبِرِیْنَ﴾ (, al-Baqarah: 153)

Translation:
O you who believe! Seek help through patience and prayer; indeed, Allah is with those who are patient.

Hadith Commentary:
➊
This means that in such circumstances, one should remain steadfast with perseverance, and no matter how the situation may be, one should not become disheartened, because cowardice and fleeing are not the qualities of a believer. And the statement of Allah, the Exalted, is:
"O you who believe! When you encounter a group (of the enemy), then stand firm, and remember Allah much, so that you may be successful." (Al-Anfal: 45/8)

➋
From this verse, it is understood that remembering Allah abundantly during battle is a means of steadfastness and the secret to success.
In the hadith, patience refers precisely to this: that by the remembrance of Allah, you keep your heart content.

Hadith Commentary:
Desiring to confront the enemy is disliked, but this is not contrary to the aspiration for martyrdom (shahadah), because the attainment of martyrdom is possible only with the support and dominance of Islam, whereas wishing for confrontation with the enemy could be contrary to this. Furthermore, the dislike for meeting the enemy applies to the person who relies solely on his own strength and considers himself great; for such a person, wishing to clash with the enemy is disliked.

(Fath al-Bari: 13/275)

In one hadith it is stated:
“Do not wish to confront the enemy, but when you do encounter them, then stand firm and face them resolutely.”
(Sahih al-Bukhari, al-Jihad wal-Siyar, Hadith: 3026)

Hadith Commentary: Benefits and Issues: In the situation of confronting the enemy, it was the noble habit of the Messenger of Allah (sallallahu alayhi wa sallam) that he would begin the battle after the morning (Fajr) prayer. This is because those Muslims who remained behind in the morning prayer would, through the supplication of Qunut Nazilah, beseech Allah for the victory and help of the Muslims and for the defeat and subjugation of the enemy. Moreover, at the time of morning, a person is fresh and alert. If it was not possible to begin the battle in the morning, then the Prophet (sallallahu alayhi wa sallam) would wait for the decline of the sun (zawal), so that the Muslims could perform Qunut Nazilah in the Dhuhr (noon) prayer, and so that the blowing of the wind would reduce the intensity and heat of the sun, and the Muslims could participate in the battle with full concentration and determination.

Al-jannah tahta zilal as-suyuf ("Paradise is under the shade of swords"): In this, with utmost brevity and in an extremely effective manner, the reward of that place is mentioned, and in an atmosphere of unity and harmony, encouragement is given to use the weaponry of that era. And finally, through supplication, by seeking the means of Allah’s help and support, the morale of the warriors is raised: that He is the One Who sent down the Book, in which there is the promise of help for the Muslims; that He is the One Who drives the clouds; that He is the Owner of perfect power; that He can use whatever apparent means of the universe He wills, and through them, He can cause the enemy to be defeated.

Benefits and Issues:
➊
War is not an ordinary game; when one is confronted with it, the reality becomes clear as to what level of faith and bravery a person possesses. Therefore, the desire should be that such an occasion does not arise at all, as that is better. However, when direct confrontation becomes inevitable, then one should place trust in Allah and display one’s full strength and courage. The desire for martyrdom (shahadah) is also of this nature: that when the opportunity arises, a person should not hesitate to risk his life. However, to give one’s life without occasion or purpose holds no meaning.

➋
“Haruri” is another name for the Khawarij. This is because when these people returned from Siffin, they separated from Ali radi Allahu anhu and gathered in the outskirts of Kufa at a place called Harura. This was their first center. Due to their association with this place, they were called Haruri.