Hebrews 3:7-11

Hebrews 3:7-11 (KJV)
7 Wherefore (as the Holy Ghost saith, To day if ye will hear his voice,
8 Harden not your hearts, as in the provocation, in the day of temptation in the wilderness:
9 When your fathers tempted me, proved me, and saw my works forty years.
10 Wherefore I was grieved with that generation, and said, They do alway err in their heart; and they have not known my ways.
11 So I sware in my wrath, They shall not enter into my rest.)

Is Once Saved, Always Saved Biblical?

The Bible is clear that there is a requirement for our lives, in order to be saved come death. That stipulation is for every believer in Christ to endure in their faith till the end.

Hebrews 3:12-14

Hebrews 3:12-14 (KJV)
12 Take heed, brethren, lest there be in any of you an evil heart of unbelief, in departing from the living God.
13 But exhort one another daily, while it is called To day; lest any of you be hardened through the deceitfulness of sin.
14 For we are made partakers of Christ, if we hold the beginning of our confidence stedfast unto the end;

Sin Hardens Our Hearts To God

The thing about sin is it is detrimental to our lives and our walk with God. Because it hardens our hearts to God and leads us to do things that are wicked, His presence is no longer in our lives either to protect us.