Standards of the Camp of Israel, according to Rabbinical Tradition

According to rabbinical tradition, the standard of Judah bore the figure of a lion, that of Reuben the likeness of a man or of a man's head, that of Ephraim the figure of an ox, and that of Dan the figure of an eagle; so that the four living creatures united in the cherubic forms described by Ezekiel were represented upon these four standards.

Keil and Delitzsch's commentary on Numbers 2:1,2

(Keil, C. F. and Delitzsch, F., Biblical Commentary on the Old Testament, var. trans. James Martin, Edinburgh: T. & T. Clark, 1865, The Pentateuch, vol. 3, pp. 17, 18.)

(Clark's Foreign Theological Library, 4th Series, vol. 6: Keil and Delitzsch on the Pentateuch, vol. 3)