The Rig Veda mentions, according to my understanding, the various stages of a spiritual aspirant, in esoteric sense.
a) advises to constantly remember any name of the AGNI, the formless Energy or Brahman.
Rig Veda 1.24.2 - Ṛṣi/seer: śunaśepa ājīgarti
अ॒ग्नेर्व॒यं प्र॑थ॒मस्या॒मृता॑नां॒ मना॑महे॒ चारु॑ दे॒वस्य॒ नाम॑ । स नो॑ म॒ह्या अदि॑तये॒ पुन॑र्दात्पि॒तरं॑ च दृ॒शेयं॑ मा॒तरं॑ च ॥
agner vayam prathamasyāmṛtānām manāmahe cāru devasya nāma | sa no mahyā aditaye punar dāt pitaraṃ ca dṛśeyam mātaraṃ ca ||
English translation
We will have to keep on thinking (cling to) the dear name of the god Agni, of the first of the immortals. He will return us to great Aditi. (Then) we would see our father and mother.
b) Explains how the DIVINE ENERGY (SOMA) flows, upon reaching the final stage
Rig Veda 9.113.8 - - Ṛṣi/seer: kaśyapa
यत्र राजा वैवस्वतो यत्रावरोधनं दिवः । यत्रामूर्यह्वतीरापस्तत्र माममृतं कृधीन्द्रायेन्दो परि स्रव ॥
yatra rājā vaivasvato yatrāvarodhanaṃ divaḥ | yatrāmūr yahvatīr āpas tatra mām amṛtaṃ kṛdhīndrāyendo pari srava ||
English translation:
Where the son of Vivasvant is king, where there is a ladder down from heaven, where those youthfully exuberant waters are, there make me immortal. – O drop, flow around for Indra.
c) The state of ONE after attaining SELF-REALISATION
When ONE attained SELF-REALISATION or merged with the BRAHMAN, one will experience all pervasiveness, immortality, oneness with the Gods, etc.
This experience was explained in 2 Hymns of Rig Veda, ie., 4.42 ( 1 to 6 Riks) and 10.125 (1 to 8 Riks).
अहमिन्द्रो वरुणस्ते महित्वोर्वी गभीरे रजसी सुमेके । त्वष्टेव विश्वा भुवनानि विद्वान्त्समैरयं रोदसी धारयं च ॥
aham indro varuṇas te mahitvorvī gabhīre rajasī sumeke | tvaṣṭeva viśvā bhuvanāni vidvān sam airayaṃ rodasī dhārayaṃ ca ||
English translation:
I, Varuṇa, am Indra. By my greatness, these two realms, wide and deep, have strong support. Like Tvaṣṭar, knowing all living beings, I pressed together the two world-halves and upheld them.
अहं राष्ट्री संगमनी वसूनां चिकितुषी प्रथमा यज्ञियानाम् । तां मा देवा व्यदधुः पुरुत्रा भूरिस्थात्रां भूर्यावेशयन्तीम् ॥
ahaṃ rāṣṭrī saṃgamanī vasūnāṃ cikituṣī prathamā yajñiyānām | tām mā devā vy adadhuḥ purutrā bhūristhātrām bhūry āveśayantīm ||
English translation:
I am ruler, assembler of goods, observer foremost among those deserving the sacrifice. Me have the gods distributed in many places—so that I have many stations and cause many things to enter (me).
