It is narrated from Jubayr bin Nufayr (may Allah have mercy on him) that Sayyiduna Umar bin al-Khattab (may Allah be pleased with him) wrote to Sayyiduna Umayr bin Sa'd al-Ansari (may Allah be pleased with him), who was the governor of Hims, instructing him to forbid the people from praying two rak'ahs after Asr. At that, Sayyiduna Abu al-Darda (may Allah be pleased with him) said: "As for me, I will not abandon them; whoever wishes to bow (that is, to refrain) may bow."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 14182