It is narrated from Sayyiduna Ibn Umar (may Allah be pleased with them both) that the Prophet (peace and blessings be upon him) made a prostration of recitation in the first rak'ah of the Zuhr prayer, and the Companions (may Allah be pleased with them) perceived that he (peace and blessings be upon him) had recited Surah al-Sajdah.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 3759