“Rapha.” Rapha was one of the Nephilim, the “Fallen Ones.” Rapha is mentioned four times in this chapter: 2 Sam. 21:16, 18, 20, and 21:22 and in other places in the Old Testament as well.
[For more on the Nephilim and the connection between them and Rapha, see commentary on Gen. 6:4.]
“spear.” The Hebrew word for “spear” is uncertain, but “spear” is a likely candidate for the word.
“300 shekels.” 300 shekels is roughly 7.5 pounds (3.4 kg). A shekel was roughly .4 ounces (11 or 11.5 grams), (see commentary on Gen. 24:22, “shekel”). A spear point that heavy would make the spear very slow when used in battle unless the person was incredibly big and strong, which Ishbi-benob was.
“being armed with a new sword,” The Hebrew does not have an object, and the scholars are divided. Some say “sword,” others “armor,” and others mention other possibilities.