Question

what is the law of karma taught by the upanishads?

Answer 1

The law of Karma is not explictly mentioned in the Samhitas of the Vedas (the part of the Vedas heard from the gods). But there's still implicit mention of it even in the Samhitas, for instance in this hymn from the Tenth Mandala of the Rig Veda, which describes the benefits of generously and liberally giving Dakshina (gifts) to the Brahmanas who have performed a Yagna (ritual) for you (Dakshina is translated with the archaic English word Guerdon meaning gift or reward):

Answer 2

• Upanishads are the philosophical texts of Hindu religion whose main principles centre around the idea of karma.
• It identifies Karma or deeds as a principle of cause and effect based on actions