Badari was a vedantin who interpreted the Upanishads. Badari is mentioned in Brahmasutra (I-2.30, III-1.11) and also in Grihya Sutra of Baudhayana and Srauta Sutra of Katyayana. In Brahmasutra (I-2.30), it is discussed as to whether in Chandogya Upanishad (V-11.18) the word vaisvanara refers to the fire int eh body, or the elemental fire or the fire deity, and whether the self mentioned therein means the individual self or the Brahman (Supreme Self). The above sutra declares that it is the Supreme Self that is meant in the context.
Badari refutes the objection that the Supreme Self cannot be
measured by a span (Chandogya Upanishad, V-18.1). He says that such a mention of
measurement of limit is intelligible because either –
the supreme self, though infinite, is yet said to be limited
by the span of the heart for the purpose of facilitating meditation by the
finite and located in the heart
the supreme self though immeasurable is yet to be meditated
on as having a measure (pradesha matra).
Karshnajini, Jaimini, Asmarathya and Shankara are in
agreement with this view. Regarding the question as to whether the karma
(deeds) of the self determines rebirth, there is the contention that it is not
karma that determines it because it is exhausted by the experiences in the other world.
The contenders quote Chandogya Upanishad (V 10, 5), and
Brihadaranyaka Upanishad (IV 4.5). They therefore suggest that it is the achara
(conduct) and not the karma (deeds) that determines rebirth.
Badari does not agree with this view. There is no difference,
according to Badari, between achara (conduct) and karma (deeds). Hence it is
karma that determines birth and not achara (Brhamasutra III – 1.11).