God's will has always been made known through His speaking -- His word. His revelation is a manifestation of His moral character. His laws, statutes, commandments, etc., are holy because He is holy (1 Pet. 1:15-16). They are true because He is truth (John 17:17; Heb. 6:18).
He spoke through prophets in previous dispensations. Holy men of God were moved by the Holy Spirit to speak the things of God (2 Pet. 1:20-21). Hebrews 1:1 states that in times past God spoke to the fathers through the prophets. He even testified of Jesus Christ before His coming to earth through the prophets (1 Pet. 1:10-11).
In this present age, God speaks exclusively through His Son (Heb. 1:1-2). The Father has delegated all authority to the Son (Matt. 28:18; Eph. 1:22-23). Jesus is that "prophet" of whom Moses spoke would be "like unto" him (Deut. 18:15; Acts 3:22). Jesus, while upon the earth, repeatedly stated that God had "sent" Him into the world (John 8:16,18,26,29,42). The apostles, over and over, declared the Lordship of Jesus (Acts 2:36; 3:26; 10:36; Eph. 1:22-23; Col. 1:18; 2:9-10). Since Jesus is God's only spokesman today, and since He possesses all authority, all teaching must be "of Christ" if it is to have proper authority behind it (2 John 9-11; 1 Tim. 6:3-5).
Using the Holy Spirit to guide them, Jesus authorized His apostles to use His authority. He promised they would receive dunamis, power (Luke 24:49; Acts 1:8). They were given exousia, authority (2 Cor. 10:8; 13:10). The Holy Spirit, as Jesus had promised, endowed them with their power and authority (John 14:26; 16:7-13).
The work of the apostles began on the day of Pentecost recorded in the second chapter of the book of Acts. Later, when they wrote, the words were given to them by the Holy Spirit (1 Cor. 2:9-13; Gal. 1:11-12).
We must respect the authority of God as it is expressed unto us by Jesus Christ since Jesus possesses all authority and since He is God's exclusive spokesman to us. If we respect His authority:
It is vitally important that every person understand how God's authority is expressed to man so that all will recognize it, learn what it commands, and submit to it in all things. To do anything less, would be to fall short of what God would have us to be and fail to live in accordance with His revealed will.