They are joined one to another - literally, "A man with his brother;" that is, each one is connected with another. There is no natural fastening of one scale with another, but they lie so close and compact that they seem thus to be fastened down on one another; see Bochart on this verse. It is this which makes the crocodile so difficult to be killed. A musket-ball will penetrate the skin under the belly, which is there less firmly protected; and accordingly the efforts of those who attempt to secure them are directed to that part of the body. A ball in the eye or throat will also destroy it, but the body is impervious to a spear or a bullet.

They are joined one to another,.... One scale to another, or "a man in his brother" (h): which may seem to favour the notion of the whale's teeth in the sockets, which exactly answer to one another; but the next clause will by no means agree with them;
they stick together, that they cannot be sundered: whereas they easily be, at least by the creature itself; but the scales of a crocodile are so closely joined and sealed together, that there is no parting them.
(h) "vir in fratre suo"; Montanus.