الإجابة
All praise be to Allah and may His blessings and peace be on His last messenger, Muhammad, Hudhayfah (R) said: “صَلَّيْتُ مَعَ النَّبِيِّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ ذَاتَ لَيْلَةٍ ، فَافْتَتَحَ الْبَقَرَةَ فَقُلْتُ يَرْكَعُ عِنْدَ الْمِائَةِ ثُمَّ مَضَى فَقُلْتُ يُصَلِّي بِهَا فِي رَكْعَةٍ فَمَضَى فَقُلْتُ يَرْكَعُ بِهَا ثُمَّ افْتَتَحَ النِّسَاءَ فَقَرَأَهَا ثُمَّ افْتَتَحَ آلَ عِمْرَانَ فَقَرَأَهَا، يَقْرَأُ مُتَرَسِّلًا إِذَا مَرَّ بِآيَةٍ فِيهَا تَسْبِيحٌ سَبَّحَ وَإِذَا مَرَّ بِسُؤَالٍ سَأَلَ وَإِذَا مَرَّ بِتَعَوُّذٍ تَعَوَّذَ“ “One night, I prayed with the Prophet (S), and he started to recite al-Baqarah and I thought: he will bow after one hundred [verses], but he carried on, so I thought that he would finish it in one rak’ahs, and he carried on. Then, he started to recite al-Nisa’ and finished it, then Aal ‘Imran and finished it, reciting all that with deliberation. When he came upon a verse of glorification, he glorified Allah; when he came upon a verse of supplication, he asked of Him; when he came upon a verse of isti’adhah (seeking refuge) with Him, he sought refuge with Him” [Muslim] Based on this hadeeth, doing that in the sunnah prayers is a sunnah. However, as for the fard, this is still allowed according to the Malikis and Hanbalis for the imam and the follower. It would be fair to say that it is allowable because those statements are not foreign to the salah. However, it is not an established sunnah to do so in the fard, since it has not been reported from the Prophet (S), even though the sahabah prayed behind him three jahri (loud) prayers daily. As for other statements, such as what you hear them say after the last verse of Surat at-Teen (Alaysa Allahu Bi Ahkamil Haakimeen), which is “Subhanak, fabala” meaning “exalted are you, most certainly,” there have been controversial reports about them, but again, they are not foreign to the corpus of salah, and may thus be said. Allah knows best.