The Messenger of Allah ﷺ was asked about the even and the odd, and he replied, "It refers to the prayer. Some of it is even and some of it is odd."
حدثنا أبو داود حدثنا همام عن قتادة عن عمران بن عصام أن شيخا حدثه من أهل البصرة
أن رسول الله ﷺ سئل عن الشفع والوتر فقال هي الصلاة بعضها شفع وبعضها وتر
Its chain is daif due to the anonymity of the narrator from Imran, since Imran bin Isam was regarded as unknown by some and accepted by others. Hakim graded the hadith sahih, though it contains Imran bin Isam, and Dhahabi agreed with him in Mustadrak 2/522. It is also found in Tirmidhi 5/440, no. 2742, where he said it is gharib, and in Tabarani's Kabir 18/232, no. 578, and in Tabari 30/172 under Surah Fajr.