“Let us therefore fear, lest, a promise being left us of entering into his rest, any of you should seem to come short of it. For unto us was the gospel preached, as well as unto them: but the word preached did not profit them, not being mixed with faith in them that heard it.” Hebrews 4:1-2 KJV
The promise to “enter in” was made to all of us and that promise still stands but some of us may fail to enter his place of rest “…because of unbelief.” Hebrews 4:6
But “we which have believed do enter into rest, as he said…” (Hebrews 4:3).
Now Hebrews 4:5,7 says,
“And in this place again, If they shall enter into my rest. Again, he [God] limiteth a certain day, saying in David, To day, after so long a time; as it is said, To day if ye will hear his voice, harden not your hearts.”
But believers are confused, not knowing who, how or what to listen – hear his voice! There are so many voices out there, that of men, angels or devils. But To day, after so long a time; as it is said, To day if ye will hear his voice, harden not your hearts.
Remember, the word of God prevailed through two periods;
1. When the word was spoken by angels
2. When the word was spoken by the Lord himself.
Whenever change happens means spiritual dynamics changes also.
I am that bread of life.  Your fathers did eat manna in the wilderness, and are dead.  This is the bread which cometh down from heaven, that a man may eat thereof, and not die.  I am the living bread which came down from heaven: if any man eat of this bread, he shall live for ever: and the bread that I will give is my flesh, which I will give for the life of the world. John 6:48-51 KJV
Remember, “there came a voice out of the cloud, saying, This is my beloved Son: hear him.” Luke 9:35
This is the bread which cometh down from heaven, that a man may eat thereof, and not die!
“For the word of God is quick, and powerful, and sharper than any twoedged sword, piercing even to the dividing asunder of soul and spirit, and of the joints and marrow, and is a discerner of the thoughts and intents of the heart.” Hebrews 4:12
When the word was spoken by the Lord himself something tremendous happened; that same ‘word of God’ suddenly became alive in us, and God mighty in us.
Whenever change happens spiritual dynamics changes also; we also were drawn nigh unto God.
Hebrews 4:14-15 says
 Seeing then that we have a great high priest, that is passed into the heavens, Jesus the Son of God, let us hold fast our profession.  For we have not an high priest which cannot be touched with the feeling of our infirmities; but was in all points tempted like as we are, yet without sin.