It can be good to study the Bible, unless we are fooling ourselves into thinking we are believing the Bible, when really we are believing our own understanding of what we thought the Bible says, and then searching for passages that support that understanding, and shying away from passages that seem to contradict those passages that we like (2 Cor.10:12).

One of the inspired writers of the Bible tells us to divide the word of truth rightly, and he tells us what that word of truth is, the gospel of your salvation (2 Tim.2:15;  Eph.1:13).

That writer of holy scripture was the only apostle commissioned by Christ to be "THE apostle of the GENTILES", Paul (Romans 11:13;  2 Tim.2:7).

Paul received Christ's latest instructions to mankind, and Christ's first instructions to allow mankind to come to Him through the gospel, instead of through Israel.  Christ initiated this gospel to all men, after Israel was no longer His people for the Gentiles to come to Him through (Hosea 1:9;  Romans 11:11).  

God's promises to, and covenants with Israel will again be in force when Israel confesses their sins to God and God forgives them and cleanses them from all unrighteousness, but God has delayed that until the fulness of the Gentiles be come into what they are coming into, the body of Christ (Romans 11:29;  1 John 1:9;  Romans 11:25;  1 Cor.12:13).

The differences between the two entities, those being Israel, and the church which is Christ's body, can be seen in Acts and in several epistles.  Those two entities can also be seen interacting with each other during that brief period of years in Acts when both entities still existed.  We can see the two different ways to be justified, by the two different gospels available AT THAT TIME.  However, only one of those two gospels still works to save us today (Acts 13:39;  Gal.2:7-9;  Gal.2:2;  2 Peter 3:15-16).

So, we can see that there really are two bodies of truth which Paul warns us to rightly divide between.  One body of truth was spoken by God to Israel, for Israel, in Israel's specific situation.  Israel's word of truth is mentioned by James in James 1:18, and described in James 2:24.  Israel's word of truth was also preached by Jesus Christ when He came as minister of the circumcision for the truth of God, to fulfull the promises made to Israel's fathers (2 Tim.2:15; James 1:18 and 2:24;  Mark 16:16;  Rom.15:8)

Israel's gospel of the circumcision came into being through God's revelations to Abram (Abraham), Moses, Jesus Christ (in His earthly ministry, before His ascension), James, John, and Peter.  It was suspended due to Israel rejecting the Kingdom and crucifying their King, Jesus Christ, and blaspheming the Holy Ghost by stoning Holy Ghost filled Stephen (Gen.12:1-3 and 15:7,18 and 17:1-14;  Exodus 19:5-8;  Rom.15:8;  James 2:24;  Gal.2:9;  Acts 10:35;  Rom.11:11-12;  Matt.12:31-32)

When Israel fell out of favor with God by rejecting their Messiah, and blaspheming the Holy Ghost (unforgiveable sin), God revealed to Paul, a new gospel, the word of truth for all people, not just Israel.  belief in Paul's gospel saves all who believe, through the gospel, not through Israel.  That gospel is God's power to save all who will believe on Him.  In whom ye also trusted, after that ye heard the word of truth, the gospel of your salvation: in whom also after that ye believed, ye were sealed with that holy Spirit of promise (Acts 22:21;  Eph.1:13).  

Since Israel was blinded and cast away at the end of Acts (28:25-29), Paul's gospel of the uncircumcision, also called the gospel of Christ, is all that remains today, belief in which saves believers today (1 Cor.15:1-4;  Gal.2:16;  Rom.5:11;  Eph.2:5-13).

When you are studying to rightly divide the word of truth, it is exciting to see the differences when you divide Paul's, all people, gospel of Christ, from Israel's gospel of the kingdom, and find the verses that define and describe the gospel of the kingdom.  Then find the verses that define and describe Paul's gospel of Christ, and see how vastly, unmistakably, totally different those two gospels are.  Study to shew thyself approved unto God, a workman that needeth not to be ashamed, rightly dividing the word of truth. (Mark 1:14-15;  Romans 1:16 and 1 Cor.15:1-4;  2 Tim.2:15). 

Mike McGlathery