1“Behold, I send my messenger, and he will prepare the way before me! The Lord, whom you seek, will suddenly come to his temple. Behold, the messenger of the covenant, whom you desire, is coming!” says Yahweh of Armies. 2“But who can endure the day of his coming? And who will stand when he appears? For he is like a refiner’s fire, and like launderers’ soap; 3and he will sit as a refiner and purifier of silver, and he will purify the sons of Levi, and refine them as gold and silver; and they shall offer to Yahweh offerings in righteousness. 4Then the offering of Judah and Jerusalem will be pleasant to Yahweh as in the days of old and as in ancient years.
5I will come near to you to judgment. I will be a swift witness against the sorcerers, against the adulterers, against the perjurers, and against those who oppress the hireling in his wages, the widow, and the fatherless, and who deprive the foreigner of justice, and don’t fear me,” says Yahweh of Armies.
6“For I, Yahweh, don’t change; therefore you, sons of Jacob, are not consumed. 7From the days of your fathers you have turned away from my ordinances and have not kept them. Return to me, and I will return to you,” says Yahweh of Armies. “But you say, ‘How shall we return?’
8Will a man rob God? Yet you rob me! But you say, ‘How have we robbed you?’ In tithes and offerings. 9You are cursed with the curse; for you rob me, even this whole nation. 10Bring the whole tithe into the storehouse, that there may be food in my house, and test me now in this,” says Yahweh of Armies, “if I will not open you the windows of heaven, and pour you out a blessing, that there will not be enough room for. 11I will rebuke the devourer for your sakes, and he shall not destroy the fruits of your ground; neither shall your vine cast its fruit before its time in the field,” says Yahweh of Armies. 12“All nations shall call you blessed, for you will be a delightful land,” says Yahweh of Armies.
13“Your words have been harsh against me,” says Yahweh. “Yet you say, ‘What have we spoken against you?’ 14You have said, ‘It is vain to serve God,’ and ‘What profit is it that we have followed his instructions and that we have walked mournfully before Yahweh of Armies? 15Now we call the proud happy; yes, those who work wickedness are built up; yes, they tempt God, and escape.’
16Then those who feared Yahweh spoke one with another; and Yahweh listened and heard, and a book of memory was written before him for those who feared Yahweh and who honored his name. 17They shall be mine,” says Yahweh of Armies, “my own possession in the day that I make. I will spare them, as a man spares his own son who serves him. 18Then you shall return and discern between the righteous and the wicked, between him who serves God and him who doesn’t serve him.
Jacob was the son of Isaac and Rebekah, born immediately after Esau, and Abraham was his grandfather. He achieved the right of the firstborn by trickery, in offering his older brother, Esau, food in exchange for the birthright, who cared little for this position. He also received the blessing of firstborn from his father Jacob before his death by cunning, and with the assistance of his mother Rebekah.
After his deception of Esau, receiving the blessing from his father, Jacob escaped to his uncle Laban, who in turn deceived Jacob into working for fourteen years for the marriage of Jacob to Leah, and then his beloved Rachel. Laban also sought to deceive Jacob of wages, but God intervened to ensure he would prosper. In a time of trial, when he feared the wrath of Esau, upon returning to the land of Canaan, Jacob had an encounter with God, and his name was changed to Israel, the one who wrestles with God. Even though his early life was characterized by deception, God worked through the situation to ensure that Jacob would be the one in the line of the patriarchs, to create a great nation and ultimately fulfill His purposes in the earth, especially through the future Messiah. The Messiah would guarantee the promise of the land to Abram and a person who would rule over Abraham's descendants, but also He would bring blessings to all the people of the earth (Gen 12:1-3).
In spite of Jacob's early failure by deception, God worked through him, and finally, Jacob became a different type of man after his struggle with God. As one has said,
"Despite Jacob’s faults, God chose him to be the leader of a great nation that still bears his name today. But for this, it is unlikely that we would know much about Jacob, who appears to be in the middle of events while the key players are those around him. There is no great wisdom or bravery in Jacob to speak of, and we are tempted to see him as little more than God’s passive instrument. If we are tempted to think that, because we aren’t in the spotlight performing great acts for God, we are unimportant to Him, then we should consider the life of Jacob and know that, in spite of our failings, God can and will still use us in His plan."
For more on Jacob, see "Who was Jacob in the Bible?", https://www.gotquestions.org/life-Jacob.html