Unbelief in Jesus Christ for that was what the Jews were pricked in their hearts for so doing. They must have been part of the mob that had crucified Jesus in unbelief. So to repent from unbelief in him by believing in Him is how one receives the remission for sins and the gift of the holy Ghost.
That is the crux of the issue. You know what the entire Christian world refuses to believe? That we are to do "all" that our heavenly Father has commanded us to do. (Luke 17:10 KJV)
It is by believing in Him is the repeated commandment for us getting the Holy Ghost at our salvation.
John 14:1Let not your heart be troubled:
ye believe in God, believe also in me. 2 In my Father's house are many mansions: if it were not so, I would have told you. I go to prepare a place for you. 3 And if I go and prepare a place for you, I will come again, and receive you unto myself; that where I am, there ye may be also. 4 And whither I go ye know, and the way ye know. 5 Thomas saith unto him, Lord, we know not whither thou goest; and how can we know the way? 6 Jesus saith unto him, I am the way, the truth, and the life: no man cometh unto the Father, but by me. 7 If ye had known me, ye should have known my Father also: and from henceforth ye know him, and have seen him. 8 Philip saith unto him, Lord, show us the Father, and it sufficeth us. 9 Jesus saith unto him, Have I been so long time with you, and yet hast thou not known me, Philip? he that hath seen me hath seen the Father; and how sayest thou then, Show us the Father?
10 Believest thou not that I am in the Father, and the Father in me? the words that I speak unto you I speak not of myself: but the Father that dwelleth in me, he doeth the works. 11
Believe me that I am in the Father, and the Father in me:
or else believe me for the very works' sake. 12 Verily, verily, I say unto you,
He that believeth on me, the works that I do shall he do also; and greater works than these shall he do; because I go unto my Father. 13 And whatsoever ye shall ask in my name, that will I do, that the Father may be glorified in the Son. 14 If ye shall ask any thing in my name, I will do it.
15 If ye love me, keep my commandments. 16 And I will pray the Father, and he shall give you another Comforter, that he may abide with you for ever; 17 Even the Spirit of truth; whom the world cannot receive, because it seeth him not, neither knoweth him: but ye know him; for he dwelleth with you, and shall be in you.
If we had to do all His commandments in order to get the promise of the Holy Ghost, then we would never get Him.
A person can stand up in church and confess he's given his heart to the Lord and now wants stop worshiping Satan, stop stealing, stop sleeping around with married women, stop lying, etc. and one after the other is met with a hearty "AMEN!!!" from the congregation....
But sinners are slaves to sin that they need to come to Jesus to deliver them from their sins and not just give them eternal life. To believe that a sinner has to repent from all sins before coming to Him is overlooking the truth that we need Him in us so we can follow Him.
....but let that man say, "And, finally, I've entered into the rest of my Savior and to demonstrate that inward rest, from now on I'm going to outwardly rest on the Sabbath after working the first six days of every week according to the fourth commandment like it says in Hebrews 4:9-10 KJV" and suddenly everyone starts shouting that he's fallen from grace.
The Jews kept the ten commandments to obtain salvation for why there can be nothing on our part in saving ourselves when our believing in Him is a work of God the Father.
John 3:18 He that believeth on him is not condemned: but he that believeth not is condemned already, because he hath not believed in the name of the only begotten Son of God. 19 And this is the condemnation, that light is come into the world, and men loved darkness rather than light, because their deeds were evil. 20 For every one that doeth evil hateth the light, neither cometh to the light, lest his deeds should be reproved. 21 But he that doeth truth cometh to the light, that his deeds may be made manifest, that they are wrought in God. Indeed, the preaching of the cross is the power of God in salvation to save those that believe in Him; not water baptism.
John 6:44 No man can come to me, except the Father which hath sent me draw him: and I will raise him up at the last day.
Matthew 11:25 At that time Jesus answered and said, I thank thee, O Father, Lord of heaven and earth, because thou hast hid these things from the wise and prudent, and hast revealed them unto babes. 26 Even so, Father: for so it seemed good in thy sight. 27 All things are delivered unto me of my Father: and no man knoweth the Son, but the Father; neither knoweth any man the Father, save the Son, and he to whomsoever the Son will reveal him.
28 Come unto me, all ye that labour and are heavy laden, and I will give you rest. 29 Take my yoke upon you, and learn of me; for I am meek and lowly in heart: and ye shall find rest unto your souls. 30 For my yoke is easy, and my burden is light.
We are to come to Him for that rest in Jesus Christ' for our salvation, not to the sabbath and not to water baptism.
John 6:37 All that the Father giveth me shall come to me; and him that cometh to me I will in no wise cast out. 38 For I came down from heaven, not to do mine own will, but the will of him that sent me. 39 And this is the Father's will which hath sent me, that of all which he hath given me I should lose nothing, but should raise it up again at the last day. 40 And this is the will of him that sent me, that every one which seeth the Son, and believeth on him, may have everlasting life: and I will raise him up at the last day.