Mundaka 3.01
तदेतत् सत्यम्।
That and this - is the truth.
यथा सुदीप्तात् पावकात् विष्फुलिङ्गाः सहस्रशः प्रभवन्ते सरूपाः। तथाऽक्षराद् विविधाः सोम्य भावाः प्रजायन्ते तत्र चैवापियन्ति ॥१॥
As from a blazing fire, sparks of a similar form arise in thousands, so, dear one, from the imperishable, various beings are born, and there indeed they merge.
दिव्यो ह्यमूर्तः पुरुषः स बाह्याभ्यन्तरो ह्यजः। अप्राणो ह्यमनाः शुभ्रो ह्यक्षरात्परतः परः ॥२॥
The divine being is formless and transcends both the external and internal realms. He is unborn, without breath or mind, pure, and exists beyond the imperishable, as the supreme entity.
Bhāshya 3.01 and 02
Three types of 'akṣara', i.e. imperishable are recognized in the scriptures - (i) the inferior imperishable is that 'Prakrti', i.e. insentient, in inert form; (ii) the supreme imperishable is 'Shri', i.e Goddess Lakshmi; and (iii) Beyond these is the Lord, supreme imperishable Vasudeva, the embodiment of supreme bliss.
"अपरं त्वक्षरं या सा प्रकृतिर्जडरूपिका। अक्षरं परमं श्रीस्तु परतः परमक्षरम्। वासुदेवः परानन्दः इति त्रिविधमक्षरम्॥"
"The inferior imperishable is that 'Prakrti', i.e. insentient, in inert form, while the supreme imperishable is 'Shri', i.e. Goddess Lakshmi. But beyond that is the supreme imperishable Vasudeva, the embodiment of supreme bliss. Thus, the imperishable is categorized into three forms."
इति च ॥२॥
- stated thus as well.