Is the Sunnah prayer limited to reciting Al-Fatiha, or is it permissible to recite short surahs in addition to Al-Fatiha?

Reciting a surah after Al-Fatihah is a Sunnah and not an obligation. So, if the worshiper limits the recitation to Al-Fatihah, their prayer is valid, whether it is an obligatory or a supererogatory prayer. This is what the four Imams, Al-Thawri, and all scholars have stated, with the exception of those who deemed the recitation of a surah along with Al-Fatihah obligatory. It is better to recite a surah after Al-Fatihah, following the example of the Prophet (peace be upon him) and to avoid disagreement.