Reference: Siyar A’laam an-Nubalaa v4 p7
Anas Ibn Seereen رحمه الله narrates on the authority of the wife of Masrooq رحمها الله, who said:
[My husband], Masrooq رحمه الله would pray [so long] until his feet swelled, and sometimes I would sit there weeping at what I saw him doing [in prolonging his prayer – causing his feet to swell].
