Isma'il bin Zayd bin Thabit (may Allah have mercy on him) relates that Sayyiduna Zayd (may Allah be pleased with him) used to pray five witr and said the salam only in the last rak'ah, and Sayyiduna Ubayy (may Allah be pleased with him) also used to do the same.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 4807