Canonical passages mentioning the 13 dhutaṅga practices I am looking for canonical passages regarding the 13 Dhutanga practices in particular Nesajjika dhutaṅga, the sitter's practice.
I doubt passages will be found in the Sutta Pitaka (discourses and sermons of the Buddha) however they are mentioned in the later Canonical texts, such as the Milinda Pañha and Mahā Niddesa.

And what are these thirteen? Wearing raiment made up of pieces taken from a dust-heap—Wearing three robes, and three robes only—Living on food received by begging—Begging straight on from house to house—Eating only once a day, at one sitting—Eating from one vessel only—Refusing food in excess of the regulations—Dwelling in the woods—Dwelling at the root of a tree-Dwelling in the open air—Dwelling in or near a cemetery—Not altering the mat or bed when it has once been spread out to sleep on—and sleeping in a sitting posture. It is he, O king, who, in former births, has undertaken and practised, followed and carried out, observed, framed his conduct according to, and fulfilled these thirteen vows, who acquires all the results of the life of a recluse, and all its ecstacy of peace and bliss becomes his very own.
Milinda Pañha Book 6 The Voluntary Extra Vows