When those who disbelieved had put into their hearts chauvinism - the (48:26)

﴿إِذْ جَعَلَ الَّذِينَ كَفَرُوا فِي قُلُوبِهِمُ الْحَمِيَّةَ حَمِيَّةَ الْجَاهِلِيَّةِ فَأَنزَلَ اللَّهُ سَكِينَتَهُ عَلَىٰ رَسُولِهِ وَعَلَى الْمُؤْمِنِينَ وَأَلْزَمَهُمْ كَلِمَةَ التَّقْوَىٰ وَكَانُوا أَحَقَّ بِهَا وَأَهْلَهَا ۚ وَكَانَ اللَّهُ بِكُلِّ شَيْءٍ عَلِيمًا﴾
[ الفتح: 26]

48:26 When those who disbelieved had put into their hearts chauvinism - the chauvinism of the time of ignorance. But Allah sent down His tranquillity upon His Messenger and upon the believers and imposed upon them the word of righteousness, and they were more deserving of it and worthy of it. And ever is Allah, of all things, Knowing.

Remember when those who disbelieved in Allah and His Messenger harboured in their hearts the pride of ignorance; an ignorance that was linked to desires and not the truth.
They haughtily rejected the entrance of the Messenger of Allah ( peace be upon him ) into Makkah the year of the treaty of Ḥudaybīyyah, fearing and blaming him that he would overpower them and take control over it.
Therefore, Allah sent down tranquility from Himself upon the His Messenger and upon the believers so their anger did not lead to them confronting the idolaters with the same actions.
Allah made the believers firm upon the statement of truth, i.
e.
‘There is none worthy of worship except for Allah’, and kept them firm upon fulfilling its rights which they fulfilled.
The believers were more worthy of this statement than others, and more deserving of it because of the goodness within their hearts that Allah knew of.
And Allah is aware of everything; nothing is hidden from Him.

When those who disbelieve had put in their hearts pride and haughtiness the pride and haughtiness of the time of ignorance, then Allah sent down His Sakinah (calmness and tranquillity) upon His Messenger (SAW) and upon the believers, and made them stick to the word of piety (i.e. none has the right to be worshipped but Allah), and they were well entitled to it and worthy of it. And Allah is the All-Knower of everything.

phonetic Transliteration

Ith jaAAala allatheena kafaroo fee quloobihimu alhamiyyata hamiyyata aljahiliyyati faanzala Allahu sakeenatahu AAala rasoolihi waAAala almumineena waalzamahum kalimata alttaqwa wakanoo ahaqqa biha waahlaha wakana Allahu bikulli shayin AAaleeman

Abdullah Yusuf Ali - Translation

While the Unbelievers got up in their hearts heat and cant - the heat and cant of ignorance,- Allah sent down His Tranquillity to his Messenger and to the Believers, and made them stick close to the command of self-restraint; and well were they entitled to it and worthy of it. And Allah has full knowledge of all things.

Safi-ur-Rahman al-Mubarakpuri

When those who disbelieve had put in their hearts pride and haughtiness -- the pride and haughtiness of the time of ignorance, -- then Allah sent down His calmness and tranquillity upon His Messenger and upon the believers, and made them stick to the word of Taqwa; and they were well entitled to it and worthy of it. And Allah is the All-Knower of everything.

Page 514 English transliteration