هُوَ الَّذِي أَنْزَلَ السَّكِينَةَ فِي قُلُوبِ الْمُؤْمِنِينَ لِيَزْدَادُوا إِيمَانًا مَعَ إِيمَانِهِمْ وَلِلَّهِ جُنُودُ السَّمَاوَاتِ وَالْأَرْضِ وَكَانَ اللَّهُ عَلِيمًا حَكِيمًا ﴿۴﴾ لِيُدْخِلَ الْمُؤْمِنِينَ وَالْمُؤْمِنَاتِ جَنَّاتٍ تَجْرِي مِنْ تَحْتِهَا الْأَنْهَارُ خَالِدِينَ فِيهَا وَيُكَفِّرَ عَنْهُمْ سَيِّئَاتِهِمْ وَكَانَ ذَلِكَ عِنْدَ اللَّهِ فَوْزًا عَظِيمًا ﴿۵﴾ وَيُعَذِّبَ الْمُنَافِقِينَ وَالْمُنَافِقَاتِ وَالْمُشْرِكِينَ وَالْمُشْرِكَاتِ الظَّانِّينَ بِاللَّهِ ظَنَّ السَّوْءِ عَلَيْهِمْ دَائِرَةُ السَّوْءِ وَغَضِبَ اللَّهُ عَلَيْهِمْ وَلَعَنَهُمْ وَأَعَدَّ لَهُمْ جَهَنَّمَ وَسَاءَتْ مَصِيرًا ﴿۶﴾

﴾4﴿ Huwal lazeee anzalas sakeenata fee quloobil mu'mineena liyazdaadooo eemaanamma'a eemaanihim; wa lillaahi junoodus samawaati wal ard; wa kaanal laahu 'Aleeman Hakeemaa
﴾5﴿ Liyudkhilal mu'mineena walmu'minaati jannaatin tajree min tahtihal anhaaru khaalideena feehaa wa yukaffira 'anhum saiyi aatihim; wa kaana zaalika 'indal laahi fawzan 'azeemaa
﴾6﴿ Wa yu'azzibal munaafiqeena walmunaafiqaati wal mushrikeena walmushrikaatiz zaaanneena billaahi zannas saw'; 'alaihim daaa'iratus saw'i wa ghadibal laahu 'alaihim wa la'anahum wa a'adda lahum jahannama wa saaa' at maseeraa

﴾4﴿ Allah, the Exalted, is the One who has sent down tranquility (certainty) into the hearts of the believers so that their faith may increase along with their existing faith. And to Allah alone belong the armies of the heavens and the earth, and Allah is All-Knowing, Most Wise
﴾5﴿ So that He may admit believing men and believing women into gardens beneath which rivers flow, where they will abide forever, and so that He may remove from them their misdeeds. And this, in the sight of Allah, is the great success
﴾6﴿ And so that He may punish the hypocrite men and hypocrite women, and the polytheist men and polytheist women—those who think evil of Allah. Upon them is the evil turn of fate; Allah's wrath is upon them, He has cursed them, and He has prepared for them Hell—a wretched destination

[4] This is the second glad tiding for the believers: the sending down of tranquility (as-sakīnah) — which refers to steadfastness in religion, peace of heart, and the removal of doubts from the heart.
Despite the hardships of the Treaty of Hudaybiyyah — such as the difficulty of travel, the disbelievers preventing them, the change of the intention from ‘Umrah to returning home, and the acceptance of certain terms of peace that outwardly appeared weak — all of these could have caused deviation or sorrow. Yet Allah removed the effects of these hardships from their hearts.

On this sending down of tranquility, four benefits are listed — the first being: (لِيَزْدَادُوا إِيمَانًا مَعَ إِيمَانِهِمْ) — "So that they may increase in faith along with their faith."
The cause of this increase in faith is that, when doubts were removed from their hearts and many miracles of the Prophet (May Allah bless him and give him peace) were manifested during the Hudaybiyyah journey, their faith necessarily increased.

There are several interpretations of this increase in faith:
The first is that it refers to belief in the laws of religion after already believing in Allah and the Last Day — this is narrated from Ibn ‘Abbas (may Allah be pleased with them both). The second opinion is that their certainty (yaqīn) in Allah and His Messenger increased even further — this is the view of Ḍaḥḥāk.
This verse is also proof that faith itself can increase and decrease. Imam Bukhari (may Allah have mercy on him) cited about eight verses like this to support this view. For example, it is well known that the certainty (yaqīn) of Abu Bakr (may Allah be pleased with him) is vastly greater than ours.
Some scholars interpret this increase in faith as an increase in actions — meaning: the more righteous actions a person performs, the greater his faith; and with fewer deeds,
[5] This is the second and third benefit that result from the descent of tranquility (as-sakīnah), which in turn leads to an increase in faith — meaning: upon this entire combination (sakīnah + increased faith), the reward of entering Paradise and the removal of sins is built.
[6] This is the fourth benefit — that the victory of the believers becomes a cause of grief and sorrow for the enemies, and this is considered a worldly punishment.
The punishment mentioned here refers to the humiliation and defeat of the hypocrites and disbelievers in this world, as well as the dominance of the believers over them — through killing, imprisoning, and subduing them.

(ظَنَّ السَّوْءِ) — they hold evil assumptions, such as believing that Allah has partners or children, or that He does not fulfill needs except through polytheistic intermediaries, or that He lacks attributes, or that His attributes are similar to those of creation. All of these are examples of evil thoughts about Allah.

(عَلَيْهِمْ دَائِرَةُ السَّوْءِ) — this refers to the worldly calamities, such as humiliation, imprisonment, defeat, and other types of punishment.