aarondarling requested more about the Spirit from the Bhagavad-Gita. Here is a passage that seems to exemplify the Gita's teaching on this subject.
[Bhagavad-Gita 6:20] When the mind is resting in the stillness of the prayer of Yoga [
yoga-sevaya, the science of union], and by the grace of the Spirit [
atmana] sees the Spirit and therein finds fulfillment;
[21] then the seeker knows the joy of Eternity: a vision seen by reason far beyond what senses can see. He abides therein and moves not from Truth.
[22] He has found joy and Truth, a vision for him supreme. He is therein steady: the greatest pain moves him not.
(trans. Juan Mascaro)
To verse 20, compare:
[Matthew 6:6] But when you pray, go into your room, close the door and pray to your Father, who is unseen. Then your Father, who sees what is done in secret, will reward you.
To verse 21, compare:
[I Corinthians 2:9] As it is written: "No eye has seen, no ear has heard, no mind has conceived what God has prepared for those who love him"
[10] --but God has revealed it to us by his Spirit.
[Acts 2:1] When the day of Pentecost came, they were all together in one place.
[2] Suddenly a sound like the blowing of a violent wind came from heaven and filled the whole house where they were sitting.
[3] They saw what seemed to be tongues of fire that separated and came to rest on each of them.
Edit: I should comment here on the mention of
grace in verse 20 above. In the esoteric tradition it is indicated that the experience of union depends upon two conditions: the readiness of the aspirant, and the descent of grace. The aspirant signals readiness by cultivating control of breath and posture and by focusing attention on the
sahasrara or crown of the head (possibly the "upstairs room" mentioned in Acts 1:13?).
This readiness however does not guarantee the descent of grace, as anyone who has spent time in contemplative prayer or meditation will tell you, it is possible to do this for months or years without any result resembling
dhyana or
samadhi. Therefore the experience of union is described always as a
revelation.