The Holy Spirit

And the angel answered and said to [Mary], "The Holy Spirit will come upon you..." Luke 1:35

From JC Ryle's commentary -

"In every step of the great work of man's redemption, we shall find special mention of the work of the Holy Ghost. Did Jesus die to make atonement for our sins? It is written that 'through tht eternal Spirit He offered Himself without spot to God.' (Heb 9:14) Did He rise again for our justification? It is written that He 'was quickened by the Spirit.' (1 Peter 3:18) Does He supply His disciples with comfort betwen the time of His first and second advent? It is written that the Comforter, whom He promised to send is 'the Spirit of truth.' (John 14:17)

"Let us take heed that we give the Holy Ghost the same place in our personal religion, which we find Him occupying in God's word. Let us remember, that all that believers have, and are, and enjoy under the Gospel, they owe to the inward teaching of the Holy Spirit. The work of each of the three Persons of the Trinity is equally and entirely needful to the salvation of every saved soul. The election of God the Father, the blood of God the Son, and the sanctification of God the Spirit, ought never to be separated in our Christianity."