Sayyiduna Jabir (may Allah be pleased with him) narrates: At first the (voluntary) night prayer was made binding upon us (Allah, the Exalted, says): "O you wrapped in garments! Stand (in prayer) at night, not just for a small part of it." So we would stand in prayer until our feet became swollen. Then Allah Almighty revealed the concession (saying): "He knows that there will be among you those who are ill" to the end of the surah.
Al-Bazzar recorded it; its chain contains Ali bin Zayd, who has been criticized but has also been declared trustworthy.