It is narrated from Sayyiduna Abdullah bin al-Zubayr (may Allah be pleased with them both) that the Messenger of Allah (peace and blessings be upon him) said: "There is no obligatory prayer except that before it there are two (voluntary) rak'ahs."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 13913
I heard Sayyiduna Abdullah bin al-Zubayr (may Allah be pleased with them both) recite this verse: "They said: These are two works of magic supporting each other" (that is, he recited it as "sihran") [Surah al-Qasas: 48].
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 13914