“making known to us the mystery of his will, according to his good pleasure that he purposed in him,” LEB
“making known to us the mystery of his will”
Paul refers to God’s will as a mystery. The mystery and will of God he is talking about, is the “mystery of Christ” (Col 2:1,2; Col 4:3), which was hidden in the Old Testament, but made known to the “holy Apostles and prophets” (Eph 3:3,4,5), and then to the Saints in Christ (Col 1:25,26,27).
Even though Christ (The Messiah) is prophesied in the Old Testament, there was a general lack of understanding regarding His death and resurrection, and salvation through Him:
“which none of the rulers of this age knew. For if they had known [it], they would not have crucified the Lord of glory.” LEB (1 Cor 2:8)
Both the Jewish and Gentile rulers were in the dark about Christ and what He came to do. They didn’t recognize Him as the Savior and King. Even the twelve disciples were confused about His death and resurrection. They didn’t fully grasp what Jesus came to do:
“for he was teaching his disciples and was telling them, “The Son of Man is being betrayed into the hands of men, and they will kill him. And [when he] is killed, after three days he will rise. But they did not understand the statement, and they were afraid to ask him.” LEB (Mark 9:31,32)
“(His disciples did not understand these [things] at first, but when Jesus was glorified, then they remembered that these [things] had been written about him and they did these [things] to him.)” LEB (John 12:16)
Many believed Jesus to be the coming King who would deliver them from Gentile rule (Mark 11:9,10). Though they were correct in regard to His Kingship, they didn’t understand that aspect very well either.
However, many believed in Him. Many believed that He was sent from God, and spoke the truth. The twelve disciples (or rather the eleven) understood that much, but their understanding regarding Christ was not complete until after His death, resurrection, and ascension. Once they received the Holy Spirit, understanding would be provided:
“These [things] I have spoken to you [while] residing with you. But the Advocate, the Holy Spirit, whom the Father will send in my name–that one will teach you all [things], and will remind you of everything that I said to you.” LEB (John 14:25,26)
“I still have many [things] to say to you, but you are not able to bear [them] now. But when he–the Spirit of truth–comes, he will guide you into all the truth. For he will not speak from himself, but whatever he hears he will speak, and he will proclaim to you the things to come. He will glorify me, because he will take from what [is] mine and will proclaim [it] to you.” LEB (John 16:12,13,14)
Thus the gospel of Jesus Christ was a mystery that wasn’t fully understood until after His resurrection and ascension, and until Pentecost (Acts 2).
This mystery was revealed to the Apostle Paul, and to the rest of the Apostles and prophets. As truth was revealed to them, it was passed on to everyone else.
A part of this mystery was the inclusion of the Gentiles with believing Jews:
“so that you may be able when you read to understand my insight into the mystery of Christ (which in other generations was not made known to the sons of men as it has now been revealed to his holy apostles and prophets by the Spirit): [that] the Gentiles are fellow heirs, and fellow members of the body, and fellow sharers of the promise in Christ Jesus through the gospel,” LEB (Eph 3:4,5,6)
We will discuss this in detail later on in our study of this book.
In summary, the mystery of which Paul spoke, is the mystery of Christ and salvation through Him, which included both Jew and Gentile, anyone who placed their faith in Him as Lord and Savior. This spiritual truth cannot be understood apart from the Holy Spirit revealing it (1 Cor 2:6-16). No one can understand the “mystery of Christ” and come to faith in Him unless the Holy Spirit opens our spiritual eyes, convicting us of our sins, and of the truth that is in Christ, and in Him alone.
“according to his good pleasure that he purposed in him,”
The “purpose in Him” is the salvation of the world through Christ. It brought pleasure to the heart of God to extend His grace to sinners in need of a Savior. Furthermore it brought pleasure to the heart of God to do it trough His Son. Even though it cost Jesus much, it was God’s good pleasure to lay upon Him the sins of the world that we might have forgiveness and life through Him:
“All we like sheep have gone astray; we have turned–every one–to his own way; and the LORD has laid on him the iniquity of us all. ” ESV (Is 53:6)
It was God’s “good pleasure” that He identify Himself with this world by becoming like one of us, in the Person of Jesus Christ. What love, what pain, what suffering, what sacrifice that represents and characterizes the heart of God for us.