It is narrated from Sayyiduna Abdullah bin Ubayd al-Thumali and Sayyiduna al-Hajjaj bin Amir al-Thumali (may Allah be pleased with them both), (both of whom were among the Companions of the Prophet (peace and blessings be upon him)), that "they both prayed the morning prayer with Sayyiduna Umar bin al-Khattab (may Allah be pleased with him), and Sayyiduna Umar (may Allah be pleased with him) recited the surah 'When the sky is split open' [Surah al-Inshiqaq: 1] and performed the prostration of recitation found in that surah."
The chain of this athar is sahih (authentic), and it indicates that prostrating during recitation in audible prayers such as Fajr is legitimate and is the practice of Umar al-Faruq.
Hadith Referenceالمطالب العالية بزوائد المسانيد الثمانية / كتاب الصلاة / 429
Hadith Gradingمحدثین:إسناده حسن
Hadith Takhrij«حکم الحدیث المطالب العالیہ محققاً تنسیق د. سعد بن ناصر بن عبد العزيز الشَّثري- مکتبہ شاملہ :إسناده حسن قال الهيثمي: رجاله موثقون ، مجمع الزوائد ومنبع الفوائد: (2 / 286) » «أورده ابن حجر فى "المطالب العالية"، 429، 3778، وأخرجه ابن أبى شيبة فى «مصنفه» برقم: 3636، 4268، 4427، وأخرجه الطبراني فى«الكبير» برقم: 3217»