Flavius Josephus, Antiquities of the Jews
William Whiston, A.M., Ed.

[272] But God persuaded him to be courageous on all occasions, and promised to be with him, and to assist him in his words, when he was to persuade men; and in his deeds, when he was to perform wonders. He bid him also to take a signal of the truth of what he said, by throwing his rod upon the ground, which, when he had done, it crept along, and was become a serpent, and rolled itself round in its folds, and erected its head, as ready to revenge itself on such as should assault it; after which it become a rod again as it was before. After this God bid Moses to put his right hand into his bosom: he obeyed, and when he took it out it was white, and in color like to chalk, but afterward it returned to its wonted color again. He also, upon God's command, took some of the water that was near him, and poured it upon the ground, and saw the color was that of blood. Upon the wonder that Moses showed at these signs, God exhorted him to be of good courage, and to be assured that he would be the greatest support to him; and bid him make use of those signs, in order to obtain belief among all men, that "thou art sent by me, and dost all things according to my commands. Accordingly I enjoin thee to make no more delays, but to make haste to Egypt, and to travel night and day, and not to draw out the time, and so make the slavery of the Hebrews and their sufferings to last the longer."