John 16:8 "And when He (Helper) has come, He will convict the world of sin, and of righteousness, and of judgment:"
All these years, the Holy Spirit was given to the Israelites as the seal of redemption just as to every born again Christian today.
Isa 63:10-11 But they rebelled and grieved His Holy Spirit; so He turned Himself against them as an enemy, and He fought against them. Then he remembered the days of old, Moses and his people, saying: "Where is He who brought them up out of the sea with the shepherd of His flock? Where is He who put His Holy Spirit within them,"
Empowering by the Holy Spirit
Gifts of wisdom, knowledge
Exo 35:30-31 And Moses said to the children of Israel, "See, the Lord has called by name Bezalel the son of Uri, the son of Hur, of the tribe of Judah; and He has filled him with the Spirit of God, in wisdom and understanding, in knowledge and all manner of workmanship.
Gift of administration:
Judge 3:10a The Spirit of the Lord came upon him, and he judged Israel.
Gift of strength and power: Judges 14:6 And the Spirit of the Lord came mightily upon him, and he tore the lion apart as one would have torn apart a young goat, though he had nothing in his hand. But he did not tell his father or his mother what he had done.
Gift of Prophecy
1Sam 19:23 So he went there to Naioth in Ramah. Then the Spirit of God was upon him also, and he went on and prophesied until he came to Naioth in Ramah.
1 Sam 16:14 But the Spirit of the Lord departed from Saul, and a distressing spirit from the Lord troubled him.
Though the Israelites were empowered with spiritual gifts by the Holy Spirit, yet they were rebellious against God and His words until King Saul lost his salvation. Without the Holy Spirit dwelling in him, evil spirit troubled or possessed him.
We thank God that for the first time He will give man the Helper or Spirit of truth. With the Holy Spirit as our Helper, we will be able to overcome the deceptions and wicked schemes of the Devil. The Helper will teach us truth so that we are set free from the world and the things therein.
All we need to do is to keep His words and commands, convincing our Lord Jesus that we sincerely want the Helper to transform us into His image. So on Pentecost in Act 2, after our Lord Jesus was raised from the death and was glorified by the Father, the Helper was given to all His disciples who had kept His words and commands.
When the Helper comes, He will convict the world of sin
Act 2:36-38 "Therefore let all the house of Israel know assuredly that God has made this Jesus, whom you crucified, both Lord and Christ." Now when they heard this, they were cut to the heart, and said to Peter and the rest of the apostles, "Men and brethren, what shall we do?" Then Peter said to them, "Repent, and let every one of you be baptized in the name of Jesus Christ for the remission of sins; and you shall receive the gift of the Holy Spirit.
Brethren, let us preach the true gospel of Jesus' crucifixion and resurrection so that the Helper or Spirit of truth will be able to convict the world of their sins and hopefully they will accept the Lord and repent of their worldliness and from dead works. As we have said before, so now I say again, if anyone preaches any other gospel to you than what you have received, let him be accursed. (Rom 1:9)