One cannot possibly understand the Bible without having an understanding of the Dispensations of God. The apostasy of the modern church in part comes from failure to understand the governance of God in the current economy leading to an ineffective (and dangerous) gospel which does not lead to salvation, along with misleading Christians in relation to the doctrine of end times (eschatology). It is vitally important to always place every verse of the Bible in its appropriate context to enable an exegesis that renders the passages as the author intended. As stated above, the gospel has been perverted so much it has become words of no-effect because men do under understand the Age of Grace, in which we are in!
A dispensation is a period of time during which God administers the affairs of His realm in a particular manner. Therefore, the definition incorporates both time and method so that during each period of time (hundreds and sometimes thousands of years) God administers the world in a particular way, and different from the previous. Thus God's will is implemented in specific and unique ways during history in order to fulfil His good purpose.
There are seven dispensations from the time of Adam until the second coming of the Messiah who reigns during the Millennium Kingdom. These are given various names although the periods are all the same. A very brief summary of each is provided below.
Man's responsibility was to obey God and not eat of the forbidden fruit in the Garden of Eden.
Man was tested by this command, which he failed for which he was judged and cast out of the garden. He could therefore not eat of the tree of life nor any more of the tree of knowledge of good and evil. Thus this dispensation ceased when Adam sinned.
Man's responsibly was to obey God set out in the Adamic Covenant (Genesis 3) which mainly had to deal with physical death – the toil to produce fruit and subjection of women to their husbands. Part of the obedience was to believe God would send the Messiah to redeem them from the prince of this world, Satan who had lied to them.
Man was tested by his conscience due to knowledge (gained when Adam took of the fruit of the tree of knowledge of good and evil). If he failed he was to provide a suitable sacrifice to God – here we see Abel succeeded and Cain failed (Hebrew 11:4). God ceased the dispensation due to the immense evil found upon the earth, vowing to kill all people, except one family - Noah.
Man's responsibly was to obey God set out in the Noahic Covenant (Genesis 9) which mainly concerned replenishing and filling the earth after the flood. The Covenant provided for the consumption of meat (up to this time only vegetable were consumed), and the establishment of civil governments. The rainbow is the sign of the Noahic Covenant.
Man failed this covenant by using the building of the Tower of Babel as its power to prevent people from moving out and populating the earth. Furthermore, empires were built under one man (Nimrod) rather than separated kingdoms as God has ordained.
Man's responsibility was to obey God set in the Abrahamic Covenant, and although it started well with Abraham leaving his native country and setting out for Canaan.
Man's failure appear to be their desire not to take procession of the Land of Canaan God had promised them. Indeed during this period, the various patriarchs left the land including Abraham who went down to Egypt, and thus the tribe of Israel ended in Egypt, enslaved.
Man's responsibility was to obey God set out in the Mosaic Law. This lengthy dispensation covers the Old Testament period of the children of Israel, from the Exodus until their consent to the death of their Messiah.
Man failed to keep the law, replaced God with idols, and latter created their own form of the law (pharisaic law) and rejecting their own Messiah, who came to save them.
Man's responsibility is (note the tense) to obey God set out in the New Covenant. This is to accept the gift (Romans 5:15) of the righteousness of God through Jesus Christ the Messiah – which is grace, obtained through faith in Yeshua (Jesus Christ) the Messiah.
Man fails in this dispensation by rejecting the gift of salvation (the gospel) which leads to death, along with failure to teach the New Covenant truths, leads to an ineffective and apostate Church. Only few will be saved from this dispensation.
Man's responsibility will be to obey God as set out in the New Covenant (salvation will be through faith) plus the ordinances of the Millennial Kingdom.
Men will fail to accept the Messiah and they will be caste into Hell with Satan at the end of the period.