गोविन्द भाष्य (श्रील बलदेव विद्याभूषण - अचिन्त्यभेदाभेद वेदान्त ब्रह्मसूत्र भाष्य सटीक)

parable of the bird in Taittirīya Upaniṣad 2.5.1 no purpose is anywhere to be seen.
What is the purpose then? The Vedas do not speak parables without a purpose
behind them.
Fearing that someone may speak these words, the author of the sūtras next
proceeds to explain the meaning of this parable of the bird.
Sūtra 15
ādhyānāya prayojanābhāvāt
ādhyānāya—for meditation; prayojana—other purpose; abhāvāt—because of
the absence.
Because of the absence of another purpose, it is for meditation.
Purport by Śrīla Baladeva Vidyābhūṣaṇa
This sūtra means, "This parable is meant for meditation. This is so because of
the absence of another purpose." The word "ādhyāna" here means "meditation".
This is the meaning. In Taittirīya Upaniṣad (2.1.2) it is said:
brahma-vid āpnoti param
"One who knows the Supreme attains the Supreme."
The Supreme is manifested in two ways: 1. in His original form, and 2. in the
forms of His pastime incarnations. In His original form the Lord has the names
Nārāyaṇa, Vāsudeva, Saṅkarṣaṇa, Pradyumna, and Aniruddha.
They whose intelligence is firmly anchored in the world of matter find it very
difficult to meditate on the Lord, who is spiritual, blissful, and all-pervading.
Therefore, in order that the conditioned souls may more easily understand the
Lord, the Taittirīya Upaniṣad describes the blissful Lord in this parable of "a bird
whose head is pleasure". In this way the conditioned souls attain elevated spiritual
intelligence and are able to meditate on the Supreme directly.
Meditation on the annamaya-puruṣa feature of the Lord is given in Taittirīya
Upaniṣad 2.1.2. Meditations on the prāṇamaya, manomaya, and vijñānamaya-
puruṣas are given in Taittirīya Upaniṣad 2.2.1, and meditation on the
Ananadamaya-puruṣa feature of the Lord is given in Taittirīya Upaniṣad 2.5.1.
These five aspects of the Supreme need not always been included in every