1 Corinthians 15.

This is the chapter wherein you will find the evidence of witnesses to the Resurrection. Oral tradition - to written. Precise timings unclear but easily within two decades of Jesus's death. 

(Modernist theologians have incorrectly put Mark's Gospel as 65AD and the other three as later.)

The works on papyrus by Carsten & Thiede debunk the modernist dates and place them considerably earlier.