Everyone makes out like it is some big mystery who God chose (elected) and why, when it is clearly shown in scripture. God chose those whom in his foreknowledge he knew would believe.
Jhn 6:64 But there are some of you that believe not. For Jesus knew from the beginning who they were that believed not, and who should betray him.
If Jesus knew from the beginning who would not believe on him, then he also knew from the beginning who would believe on him. This is confirmed in this same passage.
Jhn 6:70 Jesus answered them, Have not I chosen you twelve, and one of you is a devil?
71 He spake of Judas Iscariot the son of Simon: for he it was that should betray him, being one of the twelve.
Jesus knew from the beginning that Judas would not believe on him and would betray him (vs. 64). Jesus called Judas a devil. Therefore he also knew that the other 11 disciples would believe on him and would not betray him. He knew this when he CHOSE them.
Jesus chose Judas for the express purpose that he knew he would betray him and bring about God's purpose that Jesus would go to the cross and die for our sins. He chose the other 11 because he knew they would be believers and spread the gospel.
Jhn 17:20 Neither pray I for these alone, but for them also which shall believe on me through their word;
Jesus chose his 11 disciples and later Paul to write the scriptures and spread the gospel. Jesus knew people would believe on him through their word.
Jam 2:5 Hearken, my beloved brethren, Hath not God chosen the poor of this world rich in faith, and heirs of the kingdom which he hath promised to them that love him?
God chose the poor, because generally speaking it is the poor who are humble and trust in God, though they are poor in this material world, they are rich in faith.
1 Cor 1:26 For ye see your calling, brethren, how that not many wise men after the flesh, not many mighty, not many noble, are called:
27 But God hath chosen the foolish things of the world to confound the wise; and God hath chosen the weak things of the world to confound the things which are mighty;
28 And base things of the world, and things which are despised, hath God chosen, yea, and things which are not, to bring to nought things that are:
29 That no flesh should glory in his presence.
Why does everybody act like it is a mystery whom God has chosen and why? The scriptures are plain and simple, God has chosen the foolish people of the world, he has chosen the weak, he has chosen the base and despised to confound the mighty, the noble, and the wise, that no man may boast of himself.
The scriptures also teach us that we are elect according to the foreknowledge of the Father.
1 Pet 1:2 Elect according to the foreknowledge of God the Father, through sanctification of the Spirit, unto obedience and sprinkling of the blood of Jesus Christ: Grace unto you, and peace, be multiplied.
This verse is clear that we are elect according to the foreknowledge of the Father, something he knew before it actually came to pass. And we have seen who he chooses and why, he chooses the poor, the weak, the despised and base people who are rich in faith. This is what God saw in his foreknowledge, and this is who God chose.
It is no mystery, we are plainly told in scripture.
Look how the Lord chose Gideon to deliver Israel;
Jud 6:14 And the LORD looked upon him, and said, Go in this thy might, and thou shalt save Israel from the hand of the Midianites: have not I sent thee?
15 And he said unto him, Oh my Lord, wherewith shall I save Israel? behold, my family is poor in Manasseh, and I am the least in my father's house.
Gideon was from a poor family, and he was the least in his house. But he had faith and obeyed the Lord. This is why he was chosen.
Amos is another example:
Amo 7:14 Then answered Amos, and said to Amaziah, I was no prophet, neither was I a prophet's son; but I was an herdman, and a gatherer of sycomore fruit:
15 And the LORD took me as I followed the flock, and the LORD said unto me, Go, prophesy unto my people Israel.
Amos was not noble, wise, or mighty, he was an herdsman and a gatherer of fruit. But he believed in God and obeyed when God told him to prophesy. This is why Amos was chosen.
It is no mystery whom God chooses and why, it is plainly declared in scripture.