Tosefta zu Daniel 6:31

I would have thought that a person can pray [Shemoneh Esreh] all day long. [However] it explains in Daniel, “… and three times a day he prayed on his knees …” (Daniel 6:11) I would have thought that [a person] can pray facing any direction he wants. [However] the verse teaches us, “… where in the attic he had windows facing Yerushalayim …” (ibid.) I would have thought that [Daniel] only began to pray after he was exiled. [However] the verse teaches us, “… just as he had always done.” (ibid.)