16 Now Yishbi in Nob, who was among the descendents of Raphahh (now the weight of his spearhead was three hundredweight of bronze, and he was newly armed), said that he would kill David. 17 But Abishai the son of Zeruiah helped him, and he attacked the Philistine and killed him. Then the men of David swore to him, saying, “You shall not go out with us any longer to the battle, so that you do not quench the lamp of Israel.”
19 There was again a battle with the Philistines at Gob. And Elhanan the son of Jaare-Oregim, the Bethlehemite, killed Goliathi the Gittite, the shaft of whose spear was like the beam of a weaver.
20 Once again there was battle at Gath, and there was ⌊a man of great size⌋.j The fingers of his hand and the toes of his feet were six and six, twenty-four in number. He was also born to the Raphah. 21 He taunted Israel but Jonathan the son of Shimei, the brother of David, killed him. 22 These four were born for the Raphah in Gath, and they fell by the hand of David and by the hand of his servants.
The descendants of Raphah (i.e., the Rephaim) were thought to be giants
In view of the account of David and Goliath in 1 Sam 17, it is likely that Elhanan actually killed the brother of Goliath, Lahmi, in 1 Chr 20:5
Literally “a man of measurement”