HEB3:7 says, Wherefore (as the Holy Ghost saith, To day if ye will hear his voice,  There is the call of the Holy Spirit to all people to listen to the word of God.  Though we have the responsibility of witnessing, it is the Holy Spirit Who prepares a person to hear and calls them to believe.  Today, or any day, if we will hear the voice of the Holy Spirit calling and will accept the salvation of Christ, we shall be saved.  Verse eight states, Harden not your hearts, as in the provocation, in the day of temptation in the wilderness:  We are told to not harden our hearts, which once more says that the choice is not predestined, but is ours.  In the wilderness, those who were called God's people often hardened their hearts against Moses and God.  We are called on to not be the same way.  Verse nine says, When your fathers tempted me, proved me, and saw my works forty years.  When their fathers, or ancestors, had hardened their hearts, they tempted and proved God when He showed them His works.  Still, it cost them forty years of wandering and a generation lost, never to enter the promised land.  When we tempt or demand proof from God that He is Who He says He is, instead of simply following Him by faith, it will cost us.  When we as followers of Christ doubt Him in any given situation, we are in effect in a spiritual wilderness.  Verse ten says, Wherefore I was grieved with that generation, and said, They do alway err in their heart; and they have not known my ways.  Even after God miraculously delivered them from captivity in Egypt, a generation was lost due to a lack of faith.  We might say that this was unfair to those who did believe, but at times those who do have faith in God suffer because of the actions of those who don't.  Still, when we remain faithful to God our salvation is assured.  Even when wandering in the wilderness, God had already delivered His people from slavery in Egypt and was providing for their needs.  When God delivers us from the bondage of sin through our faith in Christ we are forever free from the power of sin.  Yet, too often we complain and allow sin to enter into our lives.  Though we are still saved if we have put our faith in Christ, we will lose some of the joy of our salvation.  The people of Israel should have been rejoicing in their deliverance, but instead thought they would have been better off enslaved than uncertain of the future.  What they should have realized, as should we, is that God already knows the future, and He has assured us everlasting life through faith in Christ.  Verse eleven declares, So I sware in my wrath, They shall not enter into my rest.)  Though the people of Israel had already been delivered physically, they still did not put their faith in God, so they lost their rest, or spiritual deliverance, through faith in Him.  Christ died for every person who ever lived or ever will live, but too many never accept so great a salvation.