by Imam Malik, translation by A'isha `Abdarahman at-Tarjumana and Ya`qub Johnson , Volume: Shortening the Prayer
Chapter: What to Do when Entering while the Imam is in Ruku
67.
Yahya related to me from Malik from Ibn Shihab that Abu Umama ibn Sahl ibn Hunayf said, "Zayd ibn Thabit entered the mosque and found the people in ruku, so he went into ruku and then moved slowly forward until he reached the row."
68.
Yahya related to me from Malik that he had heard that Abdullah ibn Masud used to move forward while in ruku.
