Ahmad recorded it (4 / 386), and its chain of transmission is good.

6. This passage is narrated by Abū Ghālib, who said: I heard Abū Umāmah say: “When you perform the ablution properly, you sit forgiven. If you then rise to pray, you will have merit and reward; and if you sit, you sit forgiven.” A man said, “O Abū Umāmah, what do you think: if he rises and prays, will it be a supererogatory act for him?” He replied, “No. A supererogatory act is only for the Prophet, peace and blessings be upon him. How could it be a supererogatory act for him when he is striving against sins and misdeeds?! Rather, he will have merit and reward.”

Ahmad recorded it (5 / 255), and its chain of transmission is good. He then recorded it (5 / 263) through the route of ʿAbd al-Ḥamīd ibn Bahrām, from Shahr ibn Ḥawshab, who said: Abū Umāmah related to me that the Messenger of Allah, peace and blessings be upon him, said: