Sri Aurobindo translates Mundaka Upanishad, Chapter 3, Section 2, Verse 9: “He, verily, who knows that Supreme Brahman becomes himself Brahman; in his lineage none is born who knows not the Brahman. He crosses beyond sorrow, he crosses beyond sin, he is delivered from the knotted cord of the secret heart and becomes immortal.”
A superficial reading of this verse creates a lot of potential for confusion or misunderstanding. In the context of all that has gone before, however, it is a relatively straightforward process to understand the Rishi’s intent here. We know that the logical intellect undertakes a secondary process based on reliance on the information provided by the senses and a process of analysis and a building up of fragments to try to understand the whole. It is thus not possible for the logical intellect to grasp the Infinity of the Supreme Brahman.
Sri Aurobindo, in The Life Divine, describes another process of knowledge which he identifies as “knowledge by identity”. This process does not take place through the methodology of the logical intellect; rather it involves a shifting of the entire standpoint of the being to become one with the “object” of knowledge, and thereby know it by “identity”. The Rishi is clearly describing “knowledge by identity” in this verse and thus, the implication that such a knower “becomes himself Brahman” is the natural outcome of knowledge by identity.
Those who take the approach that such a transition requires complete renunciation of the world and complete absorption in the unmoving Absolute, find it impossible to reconcile the next part of the verse that speaks of the results for those born of his lineage, which implies a continued involvement in the world and its manifestation. There is, however, no contradiction here when we recognize that the world is itself Brahman and an identification with Brahman does not imply the “refusal of the ascetic”; rather, it integrates the manifest and the unmanifest in a “reality omnipresent”, as Sri Aurobindo explains it.
The very fact of attaining the shift of standpoint of consciousness is bound to have an impact on those who are within the circle of relationship of the Knower, whether this is a lineage of teacher to student, or of father to child. Thus, the attainment of this status by one person will implicitly transfer to those around him.
The further implications of this transfer of status are described in the last section of the verse. Once the ego-consciousness has been released and the person identifies with the Supreme, there is no longer any cause for sorrow that results from frustrated egoistic desire fulfillment. There is also no longer any attachment to the individual form or body, as the consciousness has been universalised. Thus, death no longer has any meaning. The seeker passes beyond death and achieves immortality as the Isha Upanishad indicated as well.
Sri Aurobindo, The Upanishads, Mundaka Upanishad, pp. 193-210