Assalamualaikum ustaz. What is the status of a prayer where the imam forgot to recite the surah after al-Fatihah when he was leading the Maghrib prayer?
Alhamdulillah, praise and gratitude to Allah SWT for His countless blessings for us all. Praise and salutations to our beloved Prophet Muhammad PBUH, his family, companions and all those who follow his footsteps until the Last Day.
Prayer has its own sunnah which completes and perfect the prayer. They are divided into several parts. There is sunnah which is performed before prayer. There are matters performed in the prayer and there is also sunnah after the prayer.
For sunnah in prayer, they are divided into two:
- First, sunnah ab’adh are sunnah matters where if they are performed, it will be rewarded but if they are left, it doesn’t invalidate the prayer. However, if they are left, it is sunnah to perform sahwi prostration at the end of the prayer.
- Second, are hai’at sunnah of which when the sunnah matters are performed he will be rewarded and if they are left, it doesn’t invalidate the prayer. Likewise, sahwi prostration isn’t necessary to be performed if the hai’at sunnah is left.
Among the hai’at sunnah is to recite any surah or verses of the Quran or after reciting al-Fatihah. This is based on an athar from ‘Atha’ narrated by Ibnu Juraij, he said:
أَخْبَرَنِي عَطَاءٌ أَنَّهُ سَمِعَ أَبَا هُرَيْرَةَ رَضِيَ اللَّهُ عَنْهُ يَقُولُ فِي كُلِّ صَلَاةٍ يُقْرَأُ فَمَا أَسْمَعَنَا رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ أَسْمَعْنَاكُمْ وَمَا أَخْفَى عَنَّا أَخْفَيْنَا عَنْكُمْ وَإِنْ لَمْ تَزِدْ عَلَى أُمِّ الْقُرْآنِ أَجْزَأَتْ وَإِنْ زِدْتَ فَهُوَ خَيْرٌ
“Atha’ told me that he heard Abu Hurairah said: The Qur’an is recited in every prayer and in those prayers in which Allah’s Messenger (ﷺ) recited aloud for us, we recite aloud in the same prayers for you; and the prayers in which the Prophet (ﷺ) recited quietly, we recite quietly. If you recite “Al-Fatiha” only it is sufficient but if you recite something else in addition, it is better.” 
Al-Khatib al-Syarbini stated that reciting surah after the recitation of al-Fatihah is sunnah even if it is a short recitation. It is sunnah to recite surah for the first two rakaat. Whether it is the jahriyyah or sirriyyah prayer. As for the makmum it is not sunnah to recite surah rather it is encouraged to listen to the recitation of the surah by the imam. 
If a person leaves the recitation of surah, it isn’t necessary to perform the sahwi prostration. The reason is it is included in the hai’at sunnah. Imam al-Nawawi explained: “As for other than ab’ad sunnah, then it is not necessary for him to perform the sahwi prostration if he leaves it. This is the famous and sahih opinion.” 
This means that when a person leaves the recitation of surah or verses of the Quran after the recitation of al-Fatihah whether it is purposeful or not, then his prayer is valid and it is not necessary for him to perform sahwi prostration if he leaves it. However, if the imam forgot to recite the surah after the recitation of al-Fatihah and promptly bows, there are two situations for the makmum:
- If he is a masbuq makmum where he hasn’t had the chance to finish his recitation of al-Fatihah, then it is permissible for him to follow the imam immediately after takbiratul ihram with the duration of
- If the makmum is a muwafiq makmum, he must finish the recitation of al-Fatihah. This is based on a hadith narrated by Ubadah bin Somit where the Prophet PBUH said:
لاَ صَلاَةَ لِمَنْ لَمْ يَقْرَأْ بِفَاتِحَةِ الْكِتَابِ
“He who does not recite Fatihat al-Kitab (surah al-Fatihah) is not credited with having observed prayer.” 
In this situation, he can finish his al-Fatihah recitation and he can’t be later than three long requisites (rukun) which is the bowing, first prostration and second prostration from the imam.
Hence, in the above issue, if the imam forgets to recite surah after the recitation of al-Fatihah, then his prayer and the makmum’s is still valid. If the makmum is a masbuq makmum, then he can immediately follow the imam and bow after the takbiratul ihram with a duration of subhanallah. If he is a muwafiq makmum, then he must finish his recitation of al-Fatihah on the condition that he is not later than the imam for three long requisites (rukun).
 Narrated by al-Bukhari (772)
 See al-Iqna’ fi Hilli Alfaz Abi Syuja’, 1/142
 See Raudhah al-Talibin wa ‘Umdah al-Muftin, 1/109