The curse is here understood, as it commonly is, to maintain a greater reverence for oaths, and to beget a greater dread of the curse belonging to the violaters of it. No man is with us, i.e. here is now no man with us, who when we are parted can witness and judge between us, and punish the transgressor. Or thus, Though now we have many with us, as witnesses of this agreement, yet shortly, when we shall be parted, no man will be with us, to observe and report our actions to the other, or to do the injured person right.
Related Commentaries of Genesis 31:50
Genesis 31:50
50 If thou shalt afflict my daughters, or if thou shalt take other wives beside my daughters, no man is with us; see, God is witness betwixt me and thee.