In the Old Testament, old law times, people saw darkly, dimly, they only had prophecy in part, and they were as children, until Jesus came the first time.
Now read this next scripture, it says when perfect is comes which is in part shall be done away.
We have all the prophecies we needed, the mysteries have been revealed, they aren't in part as they once were during the Old Testament times.
10 But when that which is perfect is come, then that which is in part shall be done away.
Now read about when I was a child and what that means.
It is about being under the Old Testament times. Paul refers to that time as the people being as a child, because they didn't have Jesus yet.
Galatians 4 Now I say, That the heir, as long as he is a child, differeth nothing from a servant, though he be lord of all;
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But is under tutors and governors until the time appointed of the father.
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Even so we, when we were children, were in bondage under the elements of the world:
Did you read that? When we were children is about being under the old law.
Galatians 3:24 So the law was our guardian until Christ came that we might be justified by faith.
So now that Jesus has come, we are no longer as a child. The perfect has come.
1 Corinthians 13:11 When I was a child, I spake as a child, I understood as a child, I thought as a child: but when I became a man, I put away childish things.
We no longer see through a glass darkly, for they have seen him face to face.
12 For now we see through a glass, darkly; but then face to face: now I know in part; but then shall I know even as also I am known.
13 And now abideth faith, hope, charity, these three; but the greatest of these is charity.
See here how Peter explains it:
2 Peter 1:19 We have also a more sure word of prophecy; whereunto ye do well that ye take heed,
as unto a light that shineth in a dark place, until the day dawn, and the day star arise in your hearts:
The Old Testament believers waited a long time for God to reveal Jesus to us, and in the New Testament time people prophesied about what God finally revealed to us what He wanted us to know. We have the mysteries revealed, and we have all the teachings we need to lead us to eternal life, we cannot add or subtract from the finished work, we cannot add new prophecies and knowledge to the Bible. The perfect has come.
When you only have prophesy in part (as in the Old Testament times), the prophecy has not yet been fulfilled, and more prophecy is needed, it is imperfect. However, when there is fulfillment of prophecy (as in the New Testament times), then we have full understanding; so then, it is perfect and, that which is perfect is come.
The perfect Jesus Christ came, he gave his perfect teachings about the perfect New Covenant, he gave the perfect sacrifice, and we are made perfect by his blood and obeying his perfect words.
Hebrews 10:14 For by one sacrifice he has made perfect forever those who are being made holy.
The Bible has everything we need to know for salvation, for our being perfect.
When we have faith in Jesus’ blood and obey Jesus’ teachings, it is when and how we are made perfect.
Hebrews 5:9 and, once made perfect, he became the source of eternal salvation for all who obey him
Hebrews 10:14 because by one sacrifice he has made perfect forever those who are being made holy
Ephesians 5:26 to make her holy, cleansing her by the washing with water through the word,
James 1:25 But whoever looks intently into the perfect law that gives freedom, and continues in it—not forgetting what they have heard, but doing it—they will be blessed in what they do.
The nowadays tongue speakers claim that tongue speaking will not cease until Jesus comes again. However, we have the perfect now because Jesus came the first time, and the apostles, who were sent to lay the foundation and build upon it.
Again, Jesus the perfect came the first time, and gave the perfect law, and he is the perfect sacrifice who makes us perfect. The Bible is finished and we have Christ revealed, the mystery has been given we are no longer as children speaking as children under the old law.