Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) narrates: Two rak'ahs of the prayer of the Prophet (peace and blessings be upon him) were shorter than one rak'ah of your prayer.
Al-Tabarani recorded it in al-Mu'jam al-Kabir, and its narrators have been declared trustworthy.
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الصلاة / 2382