It is narrated from Nafi' (may Allah have mercy on him) that Ibn Umar (may Allah be pleased with them both), when he performed three rak'ahs of Witr, would say salam after two rak'ahs and then would even engage in conversation if needed.
Hadith Referenceمسند الإمام الشافعي / كتاب الصلاة / 393
Hadith Takhrijاخرجہ البخاری، الوتر، باب ما جاء فی الوتر (991)۔