I will pour upon the house of David, and upon the inhabitants of Jerusalem, the spirit of grace and of supplications: and they shall look upon me whom they have pierced, and they shall mourn for him, as one mourneth for his only son, and shall be in bitterness for him, as one that is in bitterness for his firstborn. –Zechariah 12:10 (KJV)

The Spirit also helpeth our infirmities: for we know not what we should pray for as we ought: but the Spirit itself maketh intercession for us with groanings which cannot be uttered. And he that searcheth the hearts knoweth what is the mind of the Spirit, because he maketh intercession for the saints according to the will of God. –Romans 8:26-27 (KJV)

And when they were come in, they went up into an upper room, where abode both Peter, and James, and John, and Andrew, Philip, and Thomas, Bartholomew, and Matthew, James the son of Alphaeus, and Simon Zelotes, and Judas the brother of James. These all continued with one accord in prayer and supplication, with the women, and Mary the mother of Jesus, and with his brethren. And in those days Peter stood up in the midst of the disciples, and said, (the number of names together were about an hundred and twenty,)…they were all filled with the Holy Ghost, and began to speak with other tongues, as the Spirit gave them utterance.  –Acts 1:13-15; 2:4 (KJV)

If I pray in an unknown tongue, my spirit prayeth. –1 Corinthians 14:14 (KJV)

—

Leonard Ravenhill, Why Revival Tarries.

—. Tried and Transfigured.

—. Revival Praying.

Charles Finney, Lectures on Revivals of Religion, ch. 6: “The Spirit of Prayer.”

James Goll, The Prophetic Intercessor.

John Bunyan, Prayer.

Nathaniel Vincent, The Spirit of Prayer.

William Law, The Spirit of Prayer.