(a) It is reported from Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) that the Prophet (peace and blessings be upon him) prayed two rak'ahs and recited nothing more than Surah al-Fatihah.
(b) From the words of Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both), the permissibility of sufficing with Surah al-Fatihah alone is known.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 2471