Lo, he cometh forth to the water. See Exodus 7:15, and comment. It is suspected that on this occasion Pharaoh "went to the Nile with a procession to open the solemn festival "held in the autumn when the inundation was beginning to abate (Cook).
Say unto him. Repeat, i.e; the Divine command so often given (Exodus 5:1; Exodus 7:16; Exodus 8:1).