For I delivered to you first of all that which also I received: that Christ died for our sins according to the scriptures; and that he was buried; and that he hath been raised on the third day according to the scriptures; and that he appeared to Peter; then to the Twelve; then he appeared to above five hundred brethren at once, of whom the greater part remain until now. . . .
1 Corinthians 15:3-6a (American Standard Version)
St. Paul wrote his first epistle to the Corinthians before any of the Gospels had been written; and that epistle is one of only four books in the New Testament against the genuineness and authenticity of which unbelieving criticism has found absolutely nothing to allege.
And what does St. Paul tell the Corinthians about our Lord’s resurrection? He tells them that, while he was writing, there were more than 250 persons still living who had seen our Savior on one occasion after his rising from the dead. Now here was an assertion which the Corinthians might, if they would, verify for themselves. There was enough commerce between Greece and the coast of Syria that any Corinthian who thought that St. Paul was too impetuous, or too credulous, or anything else of the kind, had only to investigate the accuracy of this statement by paying a visit to some of the 250 survivors, and cross-questioning them for himself. St. Paul’s statement was itself a challenge to do so. And if, so far as we know, the challenge was not accepted, this would only have been because men felt that unless the apostle had been quite sure of his ground, the statement would never have been made. — Henry Parry Liddon
This is not the only evidence of Christ’s resurrection from the dead, but by itself it at least meets “internet” standards of proof and is worthy of consideration.