In both the Old and New Testaments, the original Hebrew and Greek words for spirit mean wind or breath. The original words are ruach and pneuma. Spirit in the Bible is an unseen power that does things. In the same way wind is unseen, but it makes things move.
The letter to the Hebrews talks of the power in God's word to affect our thoughts and intentions:
12 For the word of God is living and active, and sharper than any two-edged sword, piercing even to the dividing of soul and spirit, of both joints and marrow, and is able to discern the thoughts and intentions of the heart.
Paul tells both the Roman and Corinthian believers that the message about Christ and his death on the cross is the power of God:
16 For I am not ashamed of the Good News of Christ, because it is the power of God for salvation for everyone who believes, for the Jew first, and also for the Greek.
18 For the word of the cross is foolishness to those who are dying, but to us who are being saved it is the power of God.
The apostle Paul tells the Thessalonian believers that it is the word of God that works in those who believe:
13 For this cause we also thank God without ceasing, that when you received from us the word of the message of God, you accepted it not as the word of men, but as it is in truth, the word of God, which also works in you who believe.
Jesus says that his words are spirit and life:
63 It is the spirit who gives life. The flesh profits nothing. The words that I speak to you are spirit, and are life.
The apostle Peter says that we are born again through the word of God:
22 Seeing you have purified your souls in your obedience to the truth through the Spirit in sincere brotherly affection, love one another from the heart fervently, 23 having been born again, not of corruptible seed, but of incorruptible, through the word of God, which lives and remains forever.
Paul says that we can be saved by understanding and obeying God breathed Scripture:
15 From infancy, you have known the holy Scriptures which are able to make you wise for salvation through faith, which is in Christ Jesus. 16 Every Scripture is God-breathed and profitable for teaching, for reproof, for correction, and for instruction in righteousness, 17 that each person who belongs to God may be complete, thoroughly equipped for every good work.
Related theme : God and Jesus Christ can be with us