Sri Baladev Vidyabhusan – the spiritual body of a liberated soul, a siddha.

In his commentary to Sri Vedanta Sutra, Sri Baladev Vidyabhusan wrote: 

The liberated soul is satya-sankalpatva. That is to say, a liberated soul possesses irrepressible willpower that enables them to achieve anything they want to achieve. They can fulfil any wish they desire, so a liberated soul can be an un-embodied being or they can have a body. Both are possible.

Liberated souls, through knowledge of Brahman, become possessed of qualities such as truthfulness of will, and become free from ignorance. Among these liberated beings, those who wilfully desire to be unembodied remain without any form. And those liberated souls who desire a spiritual form experience the manifestation of a body composed of chit-shakti in the liberated state. That manifestation of a spiritual body and the body’s continuation in that form are eternal.

The Smriti scriptures also state that all the souls dwelling in Vaikuntha possess Vaikuntha forms. In Vaikuntha, each being possesses a form composed of pure sattva, pure consciousness, and all those souls worship Shri Hari through devotion free from all worldly desires.

Read the entire commentary to Sri Vedanta Sutra 4.4 here.