When they were at the great stone which is in Gibeon, Amasa went before them. And Joab's garment that he had put on was girded unto him, and upon it a girdle with a sword fastened upon his loins in the sheath thereof; and as he went forth it fell out. Joab's garment - It appears that this was not a military garment; and that Joab had no arms but a short sword, which he had concealed in his girdle; and this sword, or knife, was so loose in its sheath that it could be easily drawn out. It is thought farther, that Joab, in passing to Amasa, stumbled, (for so some of the versions, and able critics, understand the words it fell out). and that the sword fell down when he stumbled; that he took it up with his left hand as if he had no bad intention; and then, taking Amasa by the beard with his right hand, pretending to kiss him, he, with his sword in his left hand, ripped up his bowels. This seems to be the meaning of this very obscure verse. It is worthy of remark that in the Eastern country it is the beard, not the man, which is usually kissed.
Related Commentaries of 2 Samuel 20:8
2 Samuel 20:8
8 When they were at the great stone which is in Gibeon, Amasa went before them. And Joab's garment that he had put on was girded unto him, and upon it a girdle with a sword fastened upon his loins in the sheath thereof; and as he went forth it fell out.