The Akshar Purushottam Upasana is a philosophy that establishes worshiping God along with His sadhu.
As per this philosophy, Parabrahma is Supreme God. He is the ultimate entity - the creator, sustainer, and destroyer. Akshar or Aksharbrahma is Parabrahma’s ideal devotee. Akshar remains present on Earth through the 'gunatit' ideal sadhu. God works through such an ideal sadhu.
The Sanskrit word upãsanã is a compound of two words: ‘upa’ meaning near; and ‘ãsanam’ meaning to sit. Upasana is the spiritual means for a devotee to attain an eternal place near God.
To develop complete conviction in this upasana, a devotee must develop firm faith in five truths: a) God, or Purna Purshottam Narayan, is the all-doer (sarva karta); b) He has a divine form (divya sakar); c) He is supreme and above all else (sarvopari); d) He is always present on Earth in human form (pragat); and e) the gunatit sadhu is the pathway to moksha. The essence of the Aksharbrahma-Parabrahma spiritual journey is to believe one’s self to be the atma and not this body, to become atmarup, and to worship God.
This philosophy is the foundation of the BAPS Swaminarayan Sanstha. It was revealed by Bhagwan Swaminarayan and formally established by His third spiritual successor, Shastriji Maharaj. Bhagwan Swaminarayan outlines this upasana in the Vachanamrut.