the fourth watch: The Jews at this time divided the night into four watches; the first was from six o'clock in the evening till nine, the second from nine to twelve, the third from twelve till three, and the fourth from three till six; so that it probably began to be daylight before our Lord came to his disciples. Mat 24:43; Luk 12:38
walking: This suspension of the laws of gravitation was a proper manifestation of omnipotence. Job 9:8; Psa 93:3-4, Psa 104:3; Mar 6:48; Joh 6:19; Rev 10:2, Rev 10:5, Rev 10:8