The Messenger of Allah ﷺ used to open the prayer with the takbir and begin the recitation with "Praise be to Allah, Lord of all the worlds" [Fatihah 1:2]. The hadith continues.
كان رسول الله ﷺ يستفتح الصلاة بالتكبير، والقراءة ب {الحمد لله رب العالمين}. الحديث.
Muslim narrated it in the Book of Prayer (498) from the hadith of Husayn Muallim, from Budayl bin Maysara, from Abu Jawza, from Ayesha, and he related it in full. This is correct, that they used to open the prayer with "Praise be to Allah, Lord of the worlds" [Fatihah 1:2]. As for what has been reported with the recitation of "In the name of Allah, the Most Gracious, the Most Merciful", all of it is defective. The most famous of these is the hadith of Nuaym bin Abdullah Mujmir, who said, "I prayed behind Abu Hurairah and he recited "In the name of Allah, the Most Gracious, the Most Merciful" before Umm Quran."Nasai narrated it (2/134) from Muhammad bin Abdullah bin Abdul-Hakeem, from Shuayb, who said, we were told by Layth, who said, we were told by Khalid bin Yazid, from Saeed bin Abu Hilal, from Nuaym bin Mujmir, and he related it. But Saeed bin Abu Hilal had mixed narrations.Likewise the hadith of Ibn Abbas, "The Prophet ﷺ used to open his prayer with "In the name of Allah, the Most Gracious, the Most Merciful"." Tirmidhi narrated it (245) through the route of Ismail bin Hammad, from Abu Khalid, from Ibn Abbas, and he said, "Its isnad is not up to standard." I say, this is indeed so, for Ismail bin Hammad has been criticized. Azdi said, "They criticize him," and Ibn Adi mentioned this hadith for him and then said, "It is not preserved."As for Abu Khalid, he is called Abu Khalid Walibi, and his name is Hurmuz. He was from Kufa, as Tirmidhi stated. Abu Zura was asked about Abu Khalid, the one who narrated the hadith of the basmalah from Ibn Abbas, from whom Ismail bin Hammad bin Abu Sulayman narrated, and he said, "I do not know who he is, I do not recognize him." This is how Ibn Abu Hatim mentioned it in "Kunya" in the entry for this Abu Khalid. He also mentioned him in "Asma" in the entry for Abu Khalid Walibi and named him "Hurmuz."Aqeeli said in Daifa (1/80-81), in the entry for Ismail, "His hadith is daif, and he relates it from an unknown person." Ibn Adi said, "This hadith is not narrated by anyone other than Mutamir, and it is not preserved, and Abu Khalid is unknown." See Nasb Raya (1/324).Zaylai then mentioned other routes for the hadith of Ibn Abbas from Khatib Baghdadi and others, and then quoted the words of Ibn Abdul-Hadi, who said, "The response to the hadith of Ibn Abbas can be approached from several angles.First, questioning its soundness, for isnads of this sort cannot establish a proof even if free from contradiction, let alone when they are contradicted by sahih hadiths. The soundness of an isnad depends on the reliability of the men, and even if the reliability of the men were assumed, that would not necessarily establish the soundness of the hadith until it is free of any irregularity or defect.Second, the well-known wording in its text is 'opening' rather than 'reciting aloud.'Third, his statement 'he recited aloud' only indicates that it happened once, while its continuation would require external evidence, and what has been reported that he never ceased reciting it aloud is false.Fourth, it has been reported from Ibn Abbas something that contradicts this." He then mentioned the hadith. See Nasb Raya (1/347).Likewise what has been reported from Ibn Abdullah bin Mughafal, who said, "My father heard me reciting 'In the name of Allah, the Most Gracious' and said, 'My son, this is an innovation, beware of innovation.'" He said, "I never saw anyone among the companions of the Messenger of Allah ﷺ who hated innovation in Islam more than him." He said, "I prayed with the Prophet ﷺ, and with Abu Bakr, and with Umar, and with Uthman, and I never heard any of them say it. So do not say it. When you pray, say, "Praise be to Allah, Lord of the worlds" [Fatihah 1:2]."Tirmidhi narrated it (244), and Nasai (1352), and Ibn Majah (815), all through the route of Qays bin Ubaya Abu Numama Hanafi, from Ibn Abdullah bin Mughafal, relating the same. In the version of Nasai, "I prayed behind the Messenger of Allah ﷺ, and behind Abu Bakr, and behind Umar, , and I never heard any of them recite "In the name of Allah, the Most Gracious, the Most Merciful"."Tirmidhi said, "Hasan." I say, the correct view is that it is daif, for Ibn Abdullah bin Mughafal is unknown, and no one has confirmed his reliability. His name is Yazid, as found in the version of Imam Ahmad (16787), which he related through the route of Qays bin Ubaya, relating the same. However, his name was not stated explicitly in the Sunan works, and for this reason the author of Tahdheeb did not give him an entry under the name Yazid bin Abdullah, but only mentioned him among the sons without giving him a biographical entry.Nawawi said in Khulasa (1139), after quoting from Tirmidhi that he graded the hadith hasan, "But the scholars of hadith criticized him for this and said, 'It is a daif hadith, because it revolves around Ibn Abdullah bin Mughafal, who is unknown.' Among those who stated this explicitly are Ibn Khuzayma, Ibn Abdul-Barr, Khatib Baghdadi, and others, and Tirmidhi has been accused of leniency in this regard."However, Zaylai agreed with Tirmidhi's grading of hasan, because this Yazid was narrated from by three people, and with the narration of these three the unknown status is lifted. He said, "Those who criticized him and refrained from relying on him due to the unknown status of Ibn Abdullah bin Mughafal have themselves relied, in this very issue, on something even weaker than him." End of quote, Nasb Raya (1/332).Despite all of this, an unclear status cannot be lifted except by the confirmation of one of the imams, and this Yazid bin Abdullah bin Mughafal was not given an entry by Bukhari, nor by Ibn Abu Hatim, nor by Ibn Hibban in Thiqat, despite his leniency in mentioning unknown narrators.