Reference: Siyar A’laam an-Nubalaa – Volume 11, Page 177
‘Abdullaah ibn Ahmad ibn Hanbal said:
My father would pray 300 rak’ahs every day and night, and when he became ill from having been whipped, it weakened him. [Thereafter], he would [only be able to] pray 150 rak’ahs every day and night.