Genesis 49:16-17

Dan. — In passing on to the sons of the handmaids it was necessary to assure them of an independent rank among their brethren. The four tribes descended from them did always hold an inferior position, but Jacob by his words to Dan prevented their ever becoming subject states. Playing, then, upon the name Dan (a judge), he says that he shall judge his people as a distinct and separate tribe, possessed of all those rights of self-government and tribal independence which this rank implied. It seems also that Dan’s symbol was a serpent, and from this Jacob prophesies that though too weak a tribe to take the foremost place in war, yet that Dan should not be without military importance; and this was especially the case in the days of Samson. The word rendered adder is more exactly the arrow-snake, which lies in wait in the “path,” a narrow track, and springs upon its prey as it passes. A horse bitten in this way would rear and throw its rider, who would then be in the power of his assailant.