Mark 6:46-48 NIV

46 After leaving them, he went up on a mountainside to pray.

References for Mark 6:46

47 Later that night, the boat was in the middle of the lake, and he was alone on land.
48 He saw the disciples straining at the oars, because the wind was against them. Shortly before dawn he went out to them, walking on the lake. He was about to pass by them,