اَلَمْ نَشْرَحْ لَکَ صَدْرَکَ ۙ﴿۱﴾
Did We not widen your bosom?

Tafsir al-Qurtubi تفسیر القرطبی
أَيْ أَلَمْ نَفْتَحْ صَدْرَكَ لِلْإِسْلَامِ.
i.e. did We not widen your bosom (for Islam)?

عَنِ ابْنِ عَبَّاسٍ قَالَ: قَالُوا يَا رَسُولَ اللَّهِ، أَيَنْشَرِحُ الصَّدْرُ قَالَ: [نَعَمْ وَيَنْفَسِحُ [. قَالُوا: يَا رَسُولَ اللَّهِ، وَهَلْ لِذَلِكَ عَلَامَةٌقَالَ: [نَعَمُ التَّجَافِي عَنْ دَارِ الْغُرُورِ، وَالْإِنَابَةُ إِلَى دَارِ الْخُلُودِ، وَالِاعْتِدَادُ لِلْمَوْتِ، قَبْلَ نُزُولِ الْمَوْتِ [.
Sayyiduna Ibn ‘Abbas – may Allah be pleased with them – is reported to have said: The companions asked, “O the Messenger of Allah, does the chest open?” He replied, “Yes, it does open.” They said, “Is there a sign for it, O the Messenger of Allah?” He replied, “Yes, it is withdrawal from the house of deception (the world), turning to the eternal house (the Hereafter) and preparing for death before it comes.”

وَفِي الصَّحِيحِ عَنْ أَنَسِ بْنِ مَالِكٍ، عَنْ مَالِكِ بْنِ صَعْصَعَةَ- رَجُلٍ مِنْ قَوْمِهِ- أَنَّ النَّبِيَّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ قَالَ: (فَبَيْنَا أَنَا عِنْدَ الْبَيْتِ بَيْنَ النَّائِمِ وَالْيَقِظَانِ إِذْ سَمِعْتُ قَائِلًا يَقُولُ: أَحَدُ الثَّلَاثَةِ فَأُتِيَتْ بِطَسْتٍ مِنْ ذَهَبٍ، فِيهَا مَاءُ زَمْزَمَ، فَشَرَحَ صَدْرِي إِلَى كَذَا وَكَذَا) قَالَ قَتَادَةُ قُلْتُ: مَا يَعْنِي قَالَ: إِلَى أَسْفَلِ بَطْنِي، قَالَ: [فَاسْتَخْرَجَ قَلْبِي، فَغَسَلَ قَلْبِي بِمَاءِ زَمْزَمَ، ثُمَّ أُعِيدَ مَكَانَهُ، ثُمَّ حُشِيَ إِيمَانًا وَحِكْمَةً [.
It is mentioned in Sahih Hadeeth narrated by Sayyiduna Anas ibn Malik about Malik ibn Sa’sa’ah, a man from his tribe: The Holy Prophet – may Allah send peace and blessings upon him – said: I was in a subconscious state between sleep and wakefulness by the House of Allah (the Holy Ka’bah) when I heard someone talking and he said one of the three. There was a tub made of gold containing the Zam-Zam water and they opened my chest from certain place to a certain place.” Sayyiduna Qatadah – may Allah be pleased with him – said: I asked, “What does it mean?” He replied, “To the lowest part of my stomach (and then he said), my heart was taken out and washed with ZamZam water and placed back in its spot and then it was filled with Iman and wisdom.”

وَفِي حَدِيثٍ آخَرَ قَالَ: [جَاءَنِي مَلَكٌ فَشَقَّ عَنْ قَلْبِي، فَاسْتَخْرَجَ مِنْهُ عُذْرَةً ، وَقَالَ: قَلْبُكَ وَكِيعٌ، وَعَيْنَاكَ بَصِيرَتَانِ، وَأُذُنَاكَ سَمِيعَتَانِ، أَنْتَ مُحَمَّدٌ رَسُولُ اللَّهِ، لِسَانكَ صَادِقٌ، وَنَفْسُكَ مُطْمَئِنَّةٌ، وَخُلُقُكَ قُثَمٌ، وَأَنْتَ قَيِّمٌ [.
It is mentioned in another Hadeeth that he said: An angel came and opened my heart and took it out and said: Your heart is strong, your eyes are bright, your ears are sound, you are Muhammad the Messenger of Allah, your tongue is truthful, your heart is peaceful, your character is perfect and you are guardian over the affairs.

Tafsir Qurtubi (Al-Jame’ Li Ahkaam al-Quran) Imam Shamsuddin Muhammad ibn Ahmad al-Qurtubi  D. 671 A.H.

Tafsir al-Durr al-Manthoor تفسیر الدر المنثور
عَن أبي بن كَعْب أَن أَبَا هُرَيْرَة قَالَ: يَا رَسُول الله مَا أول مَا رَأَيْت من أَمر النُّبُوَّة فَاسْتَوَى رَسُول الله صلى الله عَلَيْهِ وَسلم جَالِسا وَقَالَ: لقد سَأَلت أَبَا هُرَيْرَة إِنِّي لفي صحراء ابْن عشْرين سنة وأشهراً إِذا بِكَلَام فَوق رَأْسِي وَإِذا رجل يَقُول لرجل: أهوَ هُوَ فاستقبلاني بِوُجُوه لم أرها لخلق قطّ وأرواح لم أَجدهَا فِي خلق قطّ وَثيَاب لم أَجدهَا على أحد قطّ فَأَقْبَلَا إليّ يمشيان حَتَّى أَخذ كل وَاحِد مِنْهُمَا بعضدي لَا أجد لأخذهما مسّاً فَقَالَ أَحدهمَا لصَاحبه: أضجعه
فأضجعني بِلَا قصر وَلَا هصر فَقَالَ أَحدهمَا: افلق صَدره فخوّى أَحدهمَا إِلَى صَدْرِي ففلقه فِيمَا أرى بِلَا دم وَلَا وجع فَقَالَ لَهُ: أخرج الغل والحسد
فَأخْرج شَيْئا كَهَيئَةِ الْعلقَة ثمَّ نبذها فطرحها فَقَالَ لَهُ: أَدخل الرأفة وَالرَّحْمَة فَإِذا مثل الَّذِي أخرج شبه الْفضة ثمَّ هز ابهام رجْلي الْيُمْنَى
وَقَالَ: اغدوا سلم (اغْدُ واس
لم) فَرَجَعت بهَا أغدو بهَا رقة على الصَّغِير وَرَحْمَة للكبير
Sayyiduna Ubayi ibn Ka’b reported that Sayyiduna Abu Hurairah – may Allah be pleased with them – said: O the Messenger of Allah, what is the thing that you perceived as the first sign of Prophethood?” The Holy Prophet – may Allah send peace and blessings upon him – then sat upright and said, “O Abu Hurairah, you asked this. I was 20 years and few months old, and while I was in a desert. Out of nowhere I heard some conversation over my head, a man was saying to the other, ‘Is this the one?’ They both then headed towards me. Their faces were unlike any other faces I have seen in the entire creation and their souls were unlike any that I had come across in the creation and their garments were unlike anybody’s garments I had seen so far. They both advanced towards me and both held me by my arms but I did not feel their touch. One of them said to the other to lie me down. He laid me down without causing me any pain or discomfort. One of them said, ‘open his chest’. So he leaned forward towards my chest and opened it. I was watching all this. Neither any blood came out nor did I suffer any pain. The other said, ‘Take out the malice and jealousy’. So he took out something like a blood clot, pulled it out and threw it far away. The other one said, ‘Fill it with compassion and mercy’. Whatever amount was taken out, the same volume was placed back, it looked like silver. The big toe of my right foot was then shaken. They said, ‘Let’s go, and keep well.’ I returned in this state that I had compassion towards the young ones and mercy for the elders.”

Tafsir Al-Durr al-Manthoor Bi al-Tafsir al-Mathoor of Imam Jalaaluddin Abd al-Rahman ibn Abi Bakr al-Suyooti al-Shafe’i  D. 911 A.H.

Tafsir Rooh al-Bayaan تفسیر روح البیان
وفى الحديث إذا دخل النور فى القلب انشرح
It is mentioned in the Hadeeth: When the light (of Allah) enters the heart, the chest expands expands.

واما شرح الصدر الصوري فقد وقع مرارا
مرة وهو ابن خمس اوست لاخراج مغمز الشيطان وهو الدم الأسود الذي به يمل القلب الى المعاصي ويعرض عن الطاعات
ومرة عند ابتداء الوحى
ومرة ليلة المعراج
As for the number of times the incident of opening his chest occurred is as follows:

  1. It was opened for the first time during his childhood while he was only 5 or 6 years old, to discard the evil traits concealed in a black clot which entices the heart to commit sins and prevents from Allah’s obedience.
  2. During the beginning of revelation.
  3. In the night of Ascension (Me’raj).

ومن هنا قال المشايخ لا بد للطالب فى ابتداء امره ان يشتغل بذكر لا اله الا الله بحيث يبدأ من الجانب الايمن للصدر ويضرب بالأعلى الجانب الأيسر منه لينتقض به العلقة التي هى حظ الشيطان ومنبع الشهوات النفسانية مقدارا بعد مقدار ويمتلئ النور مقام ما ينتقض منها وربما قاء دما اسود رقيقا لا نحلاله بحرارة التوحيد وذوبانه بنار الذكر وهو من صفات الكمل فبدوام الذكر ينشرح الصدر وينفتح القلب
It is for this reason that the Mashaaikh always make it mandatory for the seeker in the beginning to engage in the Dhikr of “La Ilaha illAllah” starting from the right side of the chest and to conclude it with a strike onto the top left side of the chest in order to break the clot which is a part of devil and a hub of carnal desires, little by little, and replace it with light. Its sign is that one will vomit thin black blood from inside due to the heat of constant Dhikr which will melt it. It is the sign of Kamil Awliya and such constant Dhikr has the potential to open and expend one’s chest.

Tafsir Rooh al-Bayaan of Imam Isma’eel Haqqi ibn Mustafa al-Istanbuli Hanafi  D. 1127 A.H.