In the second portion of our text, Paul takes the phrase ---

"He was raised on the third day ---"

and amplifies it. Paul list three individuals (Peter, James,and
himself), and two groups (the other Apostles and more than
500 brothers at the same time) as eye-witnesses to the
resurrected Jesus. In Jewish and Roman Law, a minimum of two
witnesses were needed to substantiate or confirm a charge.
Therefore, Paul gives his readers overwhelming evidence the
The Resurrection of Jesus Christ did, in fact, occur!!!

From page 321, Always Growing in the Faith, by Gene Dirr.
Available at www.amazon.com.