Chapter on Times of Prayer and Sign of Each of Its Times
Tahdhīb al-Aḥkām|Volume 2|Book 1|Chapter 4
وعنه عن أحمد بن محمد قال سألته عن وقت صلاة الظهر والعصر فكتب قامة للظهر وقامة للعصر
And from him, from Ahmad ibn Muhammad, who said:
I asked Him عليه السلام about the time of the Dhuhr and ‘Asr prayers, so He عليه السلام wrote: “One forearm’s length (of shadow) for Dhuhr, and one forearm’s length for ‘Asr.”
- Tahdhīb al-Aḥkām fī Sharḥ al-Muqniʿah, vol. 2, p. 23
- Ṣaḥīḥ al-Tahdhīb