In the Gospel of Matthew, Jesus tells his disciples, "If you have faith the size of a mustard seed, you will say to this mountain, ‘Move from here to there,’ and it will move. Nothing will be impossible for you." (Matthew 17:20)
Most biblical commentators explain that Jesus is trying to illustrate a point and that he isn't challenging his disciples to start moving mountains.
However, according to a legend, there was at least one saint who took Jesus at his word.
St. Gregory the Wonderworker was a 3rd-century bishop in Caesarea who became known for his many miracles, as the Catholic Encyclopedia explains:
The many miracles that won for him the title of Thaumaturgus (Wonderworker) were doubtless performed during these years...if ever the title of "wonder-worker" was deserved, Gregory had a right to it.
The St. Andrew Daily Missal goes a step further and explains one such incident that is based on various legends of his life:
His faith was "able to move mountains," and there is a legend that he indeed obtained by his prayers, that a mountain moved to leave room for the building of a church.
There are additional stories that say he altered the course of a river, or dried-up a swamp in the area.
Whether or not these events happened historically is a matter of debate, but the truth behind the story is that St. Gregory had the faith "of a mustard seed" and trusted God in everything.
