27 Consider the lilies how they grow: they toil not, they spin not; and yet I say unto you, that Solomon in all his glory was not arrayed like one of these.
28 If then God so clothe the grass, which is to day in the field, and to morrow is cast into the oven; how much more [will he clothe] you, O ye of little faith?
29 And seek not ye what ye shall eat, or what ye shall drink, neither be ye of doubtful mind.
30 For all these things do the nations of the world seek after: and your Father knoweth that ye have need of these things.
31 But rather seek ye the kingdom of God; and all these things shall be added unto you.
32 Fear not, little flock; for it is your Father's good pleasure to give you the kingdom.
It is the Father’s good pleasure... to give us the Kingdom. I’ve written about it several times but here it is once again - the pleasure of God. Every time it is used in the New Testament with God as the subject it is in reference to Election - God choosing a bride for his church.
Verse 32 - Fear not, little flock;
How does one join into His flock? Well it matters not how much a man desires it and no lost man desires it (Romans 3:11), it depends solely on God’s mercy (Romans 9:16). He said little flock, let’s go back to His parable about sheep in John 10.
Jesus was talking to the Pharisees and He said that they do not believe because they are not His sheep. He did not say they aren’t His sheep because they do not believe - that is a huge difference. They do not believe BECAUSE they are not His sheep (John 10:26). He goes on to say that His sheep listen to Him... Yes, that means if a man does not listen, He is not one of Jesus’s sheep! The truth in this parable, as in the truths found in all the parables, a sheep is either born into the flock or the Shepherd purchases it. A sheep does not decide of its own volition to change flocks. ANY shepherd but its own shepherd is a stranger and it will flee from a stranger (John 10:5) - sounds exactly like when Jesus said a lost man will not come into the Light (John 3:20), a sheep will not go to another shepherd.
Now that we’ve established how one is placed into the flock belonging to Jesus, we can better understand what He meant when He said it is the Father’s good pleasure to give you the kingdom. It is the Father’s good pleasure to give you salvation, not because of anything we did but because of His own purpose and grace (2 Timothy 1:9), because of His mercy (Titus 3:5).
So to answer the question How does one join into the flock? Easy - a man must have been chosen in Christ before the foundation of the world (Ephesians 1:4), then it is God’s pleasure to save him. If a man wasn’t chosen, he has no hope (Ephesians 2:12, 1 Thessalonians 4:13).