It is said that this is unmanifest, inconceivable, unchangeable. Therefore, having known thus this, you should not grieve

The nature of the ātman transcends ordinary mental operations: avyaktaḥ (unmanifest, without perceptible form), acintyaḥ (inconceivable, beyond conceptual thought cintana), avikāryaḥ (without change, vi-kāra = transformation).

Ucyate (it is said) — this is the declaration of śāstra (revealed text), not the conclusion of individual logic.

The practical consequence: tasmāt (therefore) + evaṃ viditvā (having known thus) + na anuśocitum arhasi (you are not worthy of grieving). The root arh (to be worthy) implies that grieving is unworthy of one who knows the truth.