It is obvious that different people related to God in different ways in scripture. An important question to ask is why that might be? Is it that humans devised new methods for relating to God that slowly changed over time? Or was there a change on God’s part? And if the change was on God’s part in how humanity was to relate to Him, why?
First, it is obvious that God gave revelation to humanity over a reasonably long period of time. The scriptures were not given as a completed literary work, but multiple writers over hundreds of years wrote parts that came together to form the Bible. If everything written at the beginning were equally applicable to all times, why was later revelation given?
The Day of Grace
That different scripture was given for different people is evident in numerous passages, including the following samples:
“…for you are not under law but under grace.” Romans 6:14 [1]
“But if you are led by the Spirit, you are not under the law.” Galatians 5:18 [1]
God gave the law, which was clearly applicable to Israel, and equally clearly is not applicable to the church. Something has changed that delineates these two. Dispensational teaching states that this change was a change in dispensation, or stewardship in what God entrusted to mankind.
Dispensational teaching does well describe the change from Israel under the law to the present situation of believers from all nations not under the law. The Father revealed something new, sending His Son to take the place of sinners under the judgment of God to redeem the lost and perishing (e.g. Titus 2:14). There is far too much nuance in what took place in salvation to detail here; suffice it to say that God began something new in the giving of His Son that applies to all who by faith accept Him as Lord and Saviour. This new thing is well described as a new dispensation.
The Millennium
Dispensational teaching also well describes the future change that will occur at the return of the Lord Jesus Christ to earth. God again is going to make a change, by setting up a literal Kingdom under the physical reign of God the Son, that will change how mankind relates to Him.
Thinking About The Truth 