Bhagavad Gita 8.3श्री भगवानुवाच अक्षरं ब्रह्म परमं स्वभावोऽध्यात्ममुच्यते।भूतभावोद्भवकरो विसर्गः कर्मसंज्ञितः ॥

Brahman is imperishable, immutable, eternal, selfexistent, selfluminous, unchanging and allpervading. It is the source, root and womb of everything. In It all beings that are manifested live, move and have their very being. Hence, It is Paramam, the Supreme and Akshara.Its essential nature or Svabhava is Adhyatma. Brahmans dwelling in each individual body as the innermost Self (the Pratyagatma) is called Adhyatma. Yajnavalkya (a great sage of the Upanishadic period) said O Gargi Heaven and earth stand upheld in their places. The Brahmanas call this (Brahman) the Akshara (the imperishable). It is neither red nor white It is not shadow, not darkness, nor air, not ehter, without adhesion, without smell, without eyes, without ears, without speech, without mind, without light, without breath, without a mouth or door, without measures, having nothing within and nothing outside It. It does not consume anything, nor does anyone consume It. Akshara is the Supreme Brahman only.Akshara here does not mean the holy word Om, or the Avyakta (the unmanifested source of all that is in Nature). There is Laya (absorption) for Om. There is destruction for the unmanifested Nature also