In 1 Corinthians 15, Paul is speaking of the absolutely essential nature of the resurrection with regard to our faith. Along the way, he gives strong evidence for the resurrection and discusses his own “abnormal” or “untimely” spiritual birth. Tim Tebow’s own unusual birth story is well-known, so I won’t explain it here: here’s Randy Alcorn’s summary if you want details.
Tebow’s physical birth is a huge story of God’s grace and power, just like the story of Paul’s spiritual birth. This is how I worded the connection between them:
“Tim’s birth was abnormal. He almost died twice – once at the hands of the strong medicine, and once through the doctors’ medical advice. But this situation wasn’t too much for God; it wasn’t too late for Him to intervene and bring His magnificent, glorious grace to the situation. In Tim’s physical birth, and in Paul’s spiritual birth, He has shown that He is a God of great grace.”
From there, I think it is relatively easy to use both of these stories as pictures of God’s great grace in saving ALL of us. My heart was no less in need of redemption than Paul’s heart. In fact, I wasn’t preaching on 1 Corinthians 15 as my main text when I used this. I used that passage as a cross-reference to my primary text, and then I used the Tebow story.
So, this illustration could be used for a lot of passages that deal with the miracle of God’s grace: Romans 3, Romans 5, Romans 6, 1 Corinthians 15, 2 Corinthians 8:9, 2 Corinthians 9:8, Galatians 1 (also about Paul’s story), Ephesians 1, Ephesians 2, 1 Timothy 1:14, 2 Timothy 1:9, and many more.