1 Chronicles 4

The posterity of Judah by Caleb the son of Hur, #1Ch 4:1-4. By Ashur, #1Ch 4:5-8. By Jabez: his prayer, #1Ch 4:9-20. The posterity of Shelah, #1Ch 4:21-23. The posterity and cities of Simeon: their conquest of Gedor; and of the Amalekites in Mount Seir, #1Ch 4:24-43. (Pool)

In this chapter is a further account of the tribe of Judah, and of some principal families in it, #1Ch 4:1-23 and of the tribe of Simeon, their families, cities, and villages, #1Ch 4:24-38 and of the enlargement of their borders, and conquest of the Amalekites, #1Ch 4:39-43. (Gill)

9, 10. Jabez—was, as many think, the son of Coz, or Kenaz, and is here eulogized for his sincere and fervent piety, as well, perhaps, as for some public and patriotic works which he performed. The Jewish writers affirm that he was an eminent doctor in the law, whose reputation drew so many scribes around him that a town was called by his name (#1Ch 2:55); and to the piety of his character this passage bears ample testimony. The memory of the critical circumstances which marked his birth was perpetuated in his name (compare #Ge 35:15); and yet, in the development of his high talents or distinguished worth in later life, his mother must have found a satisfaction and delight that amply compensated for all her early trials. His prayer which is here recorded, and which, like Jacob's, is in the form of a vow (#Ge 28:20), seems to have been uttered when he was entering on an important or critical service, for the successful execution of which he placed confidence neither on his own nor his people's prowess, but looked anxiously for the aid and blessing of God. The enterprise was in all probability the expulsion of the Canaanites from the territory he occupied; and as this was a war of extermination, which God Himself had commanded, His blessing could be the more reasonably asked and expected in preserving them from all the evils to which the undertaking might expose him. In these words, "that it may not grieve me," and which might be more literally rendered, "that I may have no more sorrow," there is an allusion to the meaning of his name, Jabez, signifying "grief"; and the import of this petition is, Let me not experience the grief which my name implies, and which my sins may well produce. (Pool)

Pool makes some interesting poionts:

First, Jabez was a doctor in the law — that is to say, he knew the law as given to Moses.
Second, he was known for his godliness according to the law.
Third, his short prayer was a vow.
Fourth, his prayer was evidently uttered when he was entering into an important activity.
Fifth, he placed the outcome of his activity in the Lord's hands.
Sixth, evidently his activity was expelling the Canaanites from the territory he had been assigned by God in the division of the land.
Seventh, the war against the Canaanites was, therefore, waged at God's command. It was not something he was undertaking on his own.
Eighth, the blessings he pleaded for were promised by God to all who would obey the Lord's commands to drive out the enemies from one's area of responsibility.
Ninth, he had every right to expect God's blessings upon his actions, for he was acting in accord to the law-word of God.
Tenth, his prayer was that God would keep him from evil. Did he mean here the evil of defeat at the hands of the Canaanites, or the evil of sin? Regardless, he cast himself upon the providential, divine care of the Lord God.
Eleventh, his name implied grief or sorrow, v. 9. He worked at overcoming his natural tenancies, which were contrary to what was required of him by God.

In other words, there was far more involved here with Jabez than just a prayer. It included holy living, war with the enemy, and doing what was commanded by the Lord. Elijah prayed according to the will of God on Mt carmel when the rain came. So did Jabez, and both had their prayers answered, FOR THEY PRAYED ACCORDING TO THE LAW OF GOD.

Vv. 39, 40, the land where they of Ham had dwelt was taken by the sons of Simeon.

V. 43, the Amalikites who escaped the destruction that was commanded upon them are now finished off. 2 Sam. 1:8, Ex. 17:6.