God made a choice

6 The apostles and the elders were gathered together to consider this matter. 7 And after there had been much debate, Peter stood up and said to them, “ Brothers, you know that in the early days God made a choice among you, that by my mouth the Gentiles should hear the word of the gospel and believe. 8 And God, who knows the heart, bore witness to them, by giving them the Holy Spirit just as he did to us, 9 and he made no distinction between us and them, having cleansed their hearts by faith. 10 Now, therefore, why are you putting God to the test by placing a yoke on the neck of the disciples that neither our fathers nor we have been able to bear? 11 But we believe that we will be saved through the grace of the Lord Jesus, just as they will.” (Acts 15:6-11, ESV - italics added)

God made a choice ... That by, specifically, Peter's mouth... Gentiles would hear and believe, (not just some people in a general group but,) specifically Cornelius^[1] in Acts 10:30-45 as many as 10 years before the council; furthermore, God bore witness through Peter's mouth and poured out His Spirit on them. What we see here is one of the many places in scripture which God ordained to show both His sovereignty in salvific power as well as the means which He uses to do His saving work, namely the mouths/words of men. This awesome interplay leapt out of my bible at me last night. Calvin in his commentary on this passage says:

"You know. He calleth them to bear witness, ... lest any man should think that he is about to speak of some dark and doubtful thing. The history was well known to them all.....God did choose in us. The word choose doth signify to appoint or decree. Though Peter doth comprehend as well the free election of God as the choice whereby God did adopt the Gentiles to be His people; therefore, He chose, that is, as it were, making choice, that He might show a token of His free election in the Gentiles... For his meaning is, that he declareth nothing but that which they knew full well; which was done before their eyes.^[2]"

There are 5 things which I take away from this:

1. Peter addresses them with the phrase "you know" at the beginning, showing that what he is about to say, as Calvin puts it, they knew full well (Acts 15:7). This truth which is being used as an argument against Gentile circumcision, is not meant to be the focus of the passage it is almost an aside, but in nominal Christianity this aside would not, in my experience, always be a given (some would resist the free election of God which Peter uses in his argument). 
1. Application point: Do you know full well of the sovereign grace of God, or do you constantly seek to resist it (its reality or implications)?
2.  The argument is that since God freely elected to grant hearing of the word and belief to Gentiles (Acts 15:7), sealed by the outpouring of His Spirit (Acts 15:8, 10:44-45), how could those in the so called "Circumcision Party" demand that they need further physical things to keep the law for God had already poured out His Spirit? Peter makes this point of the argument clearer by stating in (Acts 15:9) that God cleansed their hearts by faith, as one who knows the heart (Acts 15:8).
1. Application point: Do you seek to add on things to your life which, if you were honest, are simply to build a resume before God who has already accepted you, if you are His, based upon the finished work of Jesus?^[3]
3. God ordained that Cornelius would hear the and believe via the mouth/words of Peter (Acts 15:7), and God is the one who bore witness to them (Acts 15:8). In back to back verses, Peter relates the interplay of the sovereignty of God and the responsibility of man. Peter says that it was his personal spoken words which he formed and spoke himself, but, on the other hand, God chose that they were to believe and bore witness to that fact by giving of His Spirit having cleansed their hearts by faith(Acts 15:9). These two doctrines are both/and; furthermore, they usually go hand in hand. It is evident that the choice of man, for which he is responsible, is certainly subordinate to God's sovereignty otherwise it could not be called sovereignty (supreme or preeminent power and authority).
1. Application point: Do you, on one side or another, tend to minimize the reality of these two truths (namely that God is preeminently sovereign and you are unequivocally responsible)?
4. James, the brother of Jesus, extends Peter's (Simeon being a different spelling for Simon whom Jesus called Peter) point to include a supporting passage from Amos 9:11-12. He expounds that God has made this choice for a reason, namely that the Gentiles, who are called by His name, would seek the Lord. The key is the appositive phrase which indicates God's personal covenantal to uphold the glory of His name (Isaiah 43:7, 48:11). God will save them for His name's sake (Psalm 106:8).
1. Application point: Do you feel more loved by God because God makes much of you, or because God, at great cost to his Son, frees you to enjoy making much of him forever? The point is the location of the bottom (last end) of your joy (is it God or is it you).^[4]
5. Finally, God, in His upholding of His name, also grants much joy to those involved in the conversion of the Gentiles. Luke chronicles this in Acts 15:3 where he intimates that great joy was brought to all the brothers when hearing of the conversion of the Gentiles (it is also safe to assume the great joy of those who began to follow Jesus, for there is no greater joy than to be united to Him).
1. Application point: Do you reach out to people desiring they have the greatest joy that exists to be had (of which you yourself are a partaker)? If not, pray to that it would be so in your life!

For His glory & your joy,
-David

[1] This inference is taken from the ESV Study Bible note on verse 7 which reads, "Peter's reference to the Gentiles hearing the gospel...by my mouth...in the early days refers to his witness at the house of Cornelius in Acts 10:34-43, c. A.D. 38, as many as 10 years before the Jerusalem council[all ellipses are from ESVSB]."

[2] Olive Tree Bible Study App. Calvin's Commentaries. "On Acts 15:7-11"

[3] If this is a point you need to work on, I suggest listening/watching this sermon.

[4] If this is a difficult question for you, please listen/watch this sermon because it should be immensely helpful.