Salamah bin al-Akwa' (may Allah be pleased with him) narrates: I said: "O Messenger of Allah! I go hunting; may I pray in a single shirt?" He (peace and blessings be upon him) said: "Yes, you may. Fasten it, even if only with a thorn."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 3294
(a) It is narrated from Yazid bin Khumayr: I heard a mawla (freed slave) of Quraysh say: I heard Abu Hurayrah (may Allah be pleased with him) narrating to Mu'awiyah (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) forbade a man to pray until he has girded his waist.
(b) Abdullah bin al-Mubarak narrates from Ibn Jurayj, who said: I was told from Yahya bin Abi Kathir that the Prophet (peace and blessings be upon him) forbade praying in a shirt whose buttons are undone, for fear that his private parts may be seen when he bows; he should fasten it.
Although this narration is munqati' (broken), it agrees with the connected narration before it.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 3295
Hadith Gradingمحدثین:منكر
Hadith Takhrij«منكر۔ اخرجه ابن سعد في الطبقات 4/ 175»
Zayd bin Aslam narrates: I saw Sayyiduna Ibn Umar (may Allah be pleased with them both) praying with the buttons of his shirt undone. I asked him about it and he said: "I saw the Messenger of Allah (peace and blessings be upon him) doing this."
Only Zuhayr bin Muhammad narrated it. It reached me from Abu Isa al-Tirmidhi that he said: I asked Muhammad, meaning al-Bukhari, about this hadith of Zuhayr, and he said: I am wary of this shaykh; it is as though his hadith is fabricated (mawdu'), and in my view this is not Zuhayr bin Muhammad. Ahmad bin Hanbal used to declare this shaykh da'if (weak) and say: This is a shaykh whose name they must have turned around. Al-Bukhari pointed to some of this in al-Tarikh.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 3296
Hadith Gradingمحدثین:صحيح لغيره
Hadith Takhrij«صحيح لغيره۔ وله طريق آخر عند البخاري في تاريخ 8/ 174۔ وسنده ايضا ضعيف»
Sa'id bin Abi Ayyub (may Allah have mercy on him) narrates: My father (may Allah have mercy on him) narrated to me: I never saw Ubaydullah bin Umar except with the buttons of his shirt undone.
Sa'id (may Allah have mercy on him) narrates: Zuhrah bin Ma'bad al-Qurashi (may Allah have mercy on him) told me: I saw Ibn al-Musayyib (may Allah have mercy on him), Abu Hazim (may Allah have mercy on him) and Muhammad bin al-Munkadir (may Allah have mercy on him); these men would pray with the buttons of their shirts undone.
It has also been reported to us from Ibn Abbas (may Allah be pleased with them both) the like of what is reported from Ibn Umar (may Allah be pleased with them both).
And when that is in prayer, in our view it is to be understood as the case where the neck opening is narrow. And Allah knows best.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 3297