Musannaf Ibn Abi Shaybah

Hazrat Harith narrates that Hazrat Mu'adh would come to his family after midday and ask them if they had anything to eat. If they apologized, Hazrat Mu'adh would say, "I will fast for the rest of the day." He would be told, "Will you fast in the last part of the day?" He would reply, "Whoever has not fasted in the last part of the day has not fasted in the first part either."