Answered by Shaykh Amjad Rasheed
If one is praying and accidentally recites some verses after the fatiha in the third rak`ah of his prayer, does this call for the prostration of forgetfulness?
This does not call for the prostration of forgetfulness, because he did not recite a verbal integral in other than its place, nor did he leave one of the main sunnas of the prayer. Rather, in our school, there is a strong position [although it is not the relied-upon position], held by Imam al-Shafi’I, may Allah be well pleased with him and have mercy on him that it is praiseworthy to recite some of the Quran in every rak`ah of the prayer.
الجواب : لا يلزم سجودُ السهو بذلك ؛ لأنه لم يقرأ ركناً قولياً في غير محله ، ولا ترك بعضاً من أبعاض الصلاة ، بل عندنا قولٌ قويٌّ لإمامنا الشافعي رضي الله عنه ورحمه : أنه يستحبُّ قراءة شيء من القرآن في كل ركعات الصلاة.