Allah said,
وَإِذَا ضَرَبْتُمْ فِى الاٌّرْضِ
(And when you Darabtum in the land,) meaning if you travel in the land. In another Ayah, Allah said,
أَن سَيَكُونُ مِنكُمْ مَّرْضَى وَءَاخَرُونَ يَضْرِبُونَ فِى الاٌّرْضِ يَبْتَغُونَ مِن فَضْلِ اللَّهِ وَءَاخَرُونَ
(He knows that there will be some among you sick, others Yadribuna (traveling) through the land, seeking of Allah's bounty...) 73:20. Allah's statement,
فَلَيْسَ عَلَيْكُمْ جُنَاحٌ أَن تَقْصُرُواْ مِنَ الصَّلوةِ
(there is no sin on you if you shorten the Salah (prayer)) by reducing (the units of the prayer) from four to two. Allah's statement,
إِنْ خِفْتُمْ أَن يَفْتِنَكُمُ الَّذِينَ كَفَرُواْ
(if you fear that the disbelievers may put you in trial (attack you)), refers to the typical type of fear prevalent when this Ayah was revealed. In the beginning of Islam, and after the Hijrah, Muslims used to experience fear during most of their travels. Rather, they restricted their movements to large or short military expeditions. During that era, most areas were areas of combatant enemies of Islam and its people. But when the prevalent circumstances cease, or a new situation is prevalent, decrees of this nature may not be understood, as Allah said;
وَلاَ تُكْرِهُواْ فَتَيَـتِكُمْ عَلَى الْبِغَآءِ إِنْ أَرَدْنَ تَحَصُّناً
(And force not your slave girls to prostitution, if they desire chastity). And His saying;
وَرَبَائِبُكُمُ اللَّـتِى فِى حُجُورِكُمْ مِّن نِّسَآئِكُمُ
(And your stepdaughters, under your guardianship, born of your wives whom you have gone into) Imam Ahmad recorded that Ya`la bin Umayyah said, "I asked `Umar bin Al-Khattab about the verse:
فَلَيْسَ عَلَيْكُمْ جُنَاحٌ أَن تَقْصُرُواْ مِنَ الصَّلوةِ إِنْ خِفْتُمْ أَن يَفْتِنَكُمُ الَّذِينَ كَفَرُواْ
(there is no sin on you if you shorten the prayer. If you fear that the disbelievers may put you in trial,) e `Allah granted Muslims safety now' `Umar said to me, `I wondered about the same thing and asked the Messenger of Allah ﷺ about it and he said,
«صَدَقَــةٌ تَصَدَّقَ اللهُ بِهَا عَلَيْكُمْ فَاقْبَلُوا صَدَقَتَه»
(A gift that Allah has bestowed on you, so accept His gift)." Muslim and the collectors of Sunan recorded this Hadith. At-Tirmidhi said, "Hasan Sahih". `Ali bin Al-Madini said, "This Hadith is Hasan Sahih from the narration of `Umar, and it is not preserved by any other route besides this one, and its narrators are all known." Abu Bakr Ibn Abi Shaybah recorded that Abu Hanzalah Al-Hadha' said, "I asked Ibn `Umar about the Qasr prayer and he said, `It consists of two Rak`ahs.' I said, what about Allah's statement,
إِنْ خِفْتُمْ أَن يَفْتِنَكُمُ الَّذِينَ كَفَرُواْ
(if you fear that the disbelievers may put you in trial (attack you),) `We are safe now.' He said, `This is the Sunnah of the Messenger of Allah ﷺ ."'. Al-Bukhari recorded that Anas said, "We went out with the Messenger of Allah ﷺ from Al-Madinah to Makkah; he used to pray two Rak`ahs until we went back to Al-Madinah." When he was asked how long they remained in Makkah, he said, "We remained in Makkah for ten days." This was recorded by the Group. Imam Ahmad recorded that Harithah bin Wahb Al-Khuza`i said, "I prayed behind the Prophet for the Zuhr and `Asr prayers in Mina, when the people were numerous and very safe, and he prayed two Rak`ahs." This was recorded by the Group, with the exception of Ibn Majah. Al-Bukhari's narration of this Hadith reads, "The Prophet led us in the prayer at Mina during the peace period by offering two Rak`ahs. "