Ibn 'Umar (May Allah be pleased with them) reported:
The Prophet (ﷺ) said, "Make Witr prayer the last of your Salat at night."[Al-Bukhari and Muslim]. (RU)
App reference (RU): Book 9, Hadith 144 (RU)
Arabic/English book reference (RU): Book 9, Hadith 1134 (RU)