Mundaka-2-1-6-tasmādṛcaḥ

Sri Shankara’s Commentary (Bhashya) translated by S. Sitarama Sastri

Com.—How? ‘Tasmat,’ from the Purasha; ‘Richah the mantras whose letters, feet and endings are determined and which are marked by Chhandas (metre) like the gayatri. Sama with its fivefold and sevenfold classification characterized by sthoba and other gita (music). ‘Yajus,’ mantras in the form of sentences, whose letters, feet and endings are determined by no rules. Thus the threefold mantras. ‘Diksha’, restrictions such as the wearing of a mounjee (a kind of cord), etc., imposed upon the performer (of a sacrifice). ‘Yajnas,’ all sacrifices such as Agnihotra, etc. ‘Kratu’ sacrifices which require a yupa (i.e., sacrificial post). ‘Dakshinah,’ rewards distributed in sacrifice from a single cow up to unbounded whole wealth. ‘Year,’ stated time as a necessary adjunct of karma. ‘Yajamano’ the performer, i.e., the sacrificer. The worlds which are the fruits of his karma are next described “which the moon renders sacred and where the sun shines”; these are attainable by the northern and southern routes and are the fruits of the karma performed by the knowing and the ignorant.

Links
Various resources on the Mundakopanishad
Upanishad Series – Mundakopanishad Commentary by Swami Chinmayananda