God had never had a 'gift or calling' of unconditional salvation, so a 'gift or calling' that never occurred cannot be irrevocable.
Rom 11:28 "As concerning the gospel, they are enemies for your sakes: but as touching the election, they are beloved for the fathers' sakes."
Rom 11:29 "For the gifts and calling of God are without repentance."
In the context of Romans 11:29 God had cast of his once chosen nation of Israel due to their disobedience not obeying Christ as the Messiah. (No OSAS for them). God grafted in the Gentiles.
Verse 28 concerning the gospel they (the Jews that refused to believe Christ) are enemies for your (Gentiles) sake. For the Jews rejection of Christ and the gospel brought the gospel to the Gentiles that much sooner (Acts 13:46). The Jews that rejected Christ were 'enemies' to the believing Gentiles.
Touching the election, they (the unbelieving Jews) can still be of the elect due to God's love for the fathers' (Abraham, Isaac,Jacob) sake. So even though God cast of the nation of Israel, God did not make salvation an impossibility for them.
Verse 29 "for" an explanatory preposition giving explanation as to why the unbelieving Jews still can be saved even though God cast them off.
"....the gifts and calling of God are without repentance". Back in Genesis God promised that through Abraham all nations would be blessed, this "all nations" includes the nation of Israel and the gospel is for every nation, every creature (Great Commission) which also includes the nation of Israel. But if God cast the nation of Israel off to the point that salvation was not attainable for them, then God would have to repent (change) and revoke what He said to Abraham and revoke the Great Commission. But since God still left election open for the Jews to be saved through Christ (even though the majority rejected Christ) God is keeping what He said and not changing it...God's offer for salvation still stands for all men and that is not going to be revoked.
Nothing remotely about the man made idea of OSAS here at all.
Some of Israel did not receive Him (Lord Jesus). But our Father's plan for that nation has not been canceled.I don't know how He will accomplish His will, but I trust that His perfect will will be accomplished. As far as my salvation, I know Him in whom I have placed my trust.No amount of humanism/self righteousness that you guys are preaching is going to make me doubt Him. I know that Lord Jesus is my Savior, and my Lord, my God. The Bible teaches us that all of our righteousness is as a filthy rag. ( a nasty stinky, menstrul cloth). I trust His righteousness that has been imputed to me at my salvation. It is God working His will in my by the Holy Ghost. I know that I am saved by the witness of two, the Word and the Holy Ghost. Neither of them have lied.God has not given me the Spirit of fear.
2 Timothy 1:7 For God hath not given us the spirit of fear; but of power, and of love, and of a sound mind.
Neither have I received a spirit of bondage which it seems you guys are forcing on to those who do not know who they are in Christ. Shame on you,for you do not preach the truth of the gospel.
Romans 8:15 For ye have not received the spirit of bondage again to fear; but ye have received the Spirit of adoption, whereby we cry, Abba, Father.
Lord Jesus said the Holy Ghost will remain in us
forever. Christ in me, keeping me, guiding me, teaching me through His word,is my hope of glory. You guys with your works righteousness, have at it.
16 The Spirit itself beareth witness with our spirit, that we are the children of God: