Jamieson, Fausset and Brown on Joshua 4:19

19. the people came up out of Jordan on the tenth day of the first month--that is, the month Nisan, four days before the passover, and the very day when the paschal lamb required to be set apart, the providence of God having arranged that the entrance into the promised land should be at the feast.

and encamped in Gilgal--The name is here given by anticipation (see on Jos 5:9). It was a tract of land, according to Josephus, fifty stadia (six and one-half miles) from Jordan, and ten stadia (one and one-fourth miles) from Jericho, at the eastern outskirts of the palm forest, now supposed to be the spot occupied by the village Riha.