In the Gospel of John, why does Jesus say (four times), “I will raise him up at the last day”?

It’s obviously significant since he repeated it four times, but what actually is the significance of the phrase? The phrase is translated from the Greek ἀναστήσω αὐτὸ (ἐν) τῇ ἐσχάτῃ ἡμέρᾳ which occurs in the following four verses: John …