Habib al-Mu'allim (may Allah have mercy on him) says that it was said to al-Hasan (may Allah have mercy on him) that Ibn Umar (may Allah be pleased with them both) used to say the salam after two rak'ahs of the witr. He said: Sayyiduna Umar (may Allah be pleased with him) had more understanding than him; he used to rise for the third rak'ah with the takbir.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 4808