Jamieson, Fausset & Brown

Master--betokening not surely a first acquaintance, but a relationship already formed. all night--the usual time of fishing then (Joh 21:3), and even now Peter, as a fisherman, knew how hopeless it was to "let down his net" again, save as a mere act of faith, "at His word" of command, which carried in it, as it ever does, assurance of success. (This shows he must have been already and for some time a follower of Christ.)