In 1 Corinthians 15, Paul preaches the same Gospel message as Christ in Luke 24:40ff.
Paul also quotes the Lord here in 1 Corinthians 11:
1 Corinthians 11: KJV
23 For I have received of the Lord that which also I delivered unto you, that the Lord Jesus the same night in which he was betrayed took bread:
24 And when he had given thanks, he brake it, and said, Take, eat: this is my body, which is broken for you: this do in remembrance of me.
25 After the same manner also he took the cup, when he had supped, saying, this cup is the new testament in my blood: this do ye, as oft as ye drink it, in remembrance of me.
The apostle Paul stated he was taught directly by Jesus Christ :
Galatians 1: KJV
11 But I certify you, brethren, that the gospel which was preached of me is not after man.
12 For I neither received it of man, neither was I taught it, but by the revelation of Jesus Christ.
13 For ye have heard of my conversation in time past in the Jews' religion, how that beyond measure I persecuted the church of God, and wasted it:
14 And profited in the Jews' religion above many my equals in mine own nation, being more exceedingly zealous of the traditions of my fathers.
15 But when it pleased God, who separated me from my mother's womb, and called me by his grace,
16 To reveal his Son in me, that I might preach him among the heathen; immediately I conferred not with flesh and blood:
17 Neither went I up to Jerusalem to them which were apostles before me; but I went into Arabia, and returned again unto Damascus.
18 Then after three years I went up to Jerusalem to see Peter, and abode with him fifteen days.
19 But other of the apostles saw I none, save James the Lord's brother.
20 Now the things which I write unto you, behold, before God, I lie not.
21 Afterwards I came into the regions of Syria and Cilicia;
22 And was unknown by face unto the churches of Judaea which were in Christ:
23 But they had heard only, That he which persecuted us in times past now preacheth the faith which once he destroyed.
24 And they glorified God in me.
Taking into consideration the above, one can only come to two conclusions:
1. Paul is faithfully delivering the message of Jesus Christ.
2. Paul is deceiving the Galatians.
There is no wiggle room here. Paul threw down the gauntlet in Galatians chapter 1.
So what is it? #1 or #2?