It is narrated from Sayyiduna Abdur Rahman bin Abza that the Prophet (peace and blessings be upon him) used to recite Surah Sabbihisma Rabbikal A'la, Surah Kafiroon, and Surah Ikhlas in Witr, and after saying salam, he would say "Subhanal Malikil Quddus" three times in a raised voice.
Hadith Referenceمسند احمد / مسند المكيين / 15356
Hadith Gradingحکم دارالسلام:حديث صحيح، لم يذكر سماع زرارة من عبدالرحمن بن أبزى، لكنه توبع