Why did John the babtist started baptising?

Nothing, salvation has nothing to do with water baptism.

So in the end, you are saying whether one stays saved, depends on whether he is prepared to be water baptized after he got saved by faith alone?

Im saying that Jesus says we are to be baptised, and we should obey him. Its not that complicated as you are making it out to be.

Mine is even less complicated. You are reading the wrong mail. You assume that when Jesus told Israel that all of them must be water baptized, it is also written to you as well.

Imagine if someone tell you "God told Noah to build an ark, since I believe God is telling that to every believer, I will go ahead and build an ark too".

How would you respond to that?

Jesus said his desciples were to go into all nations and baptise them. Gentiles are included in the "all nations."

Christ offers salvation for every one of our sins, but we are to repent of those sins we ask forgiveness for. It is not water baptism that Christ asks us for, it is spiritual baptism. We can tell Christ no, I don't want to be baptized spiritually, and not repent of that decision. Then we are also telling Christ no, I don't repent.

Gentiles are included in the "all nations." is one of the popular misinterpretations of the Matthew's version of the GC.

Peter's response to Cornelius in Acts 10:28 and his explanation to the Jewish believers in Acts 11 would make no sense, if that was how Matthew 28 was to be understood.

I agree that we are changed with the Spiritual baptism, but the preceding water baptism changing an individual depends upon that individual if he continues to earnestly want to leave his sins behind in order to get closer to God. If, however, after going through a water baptism, an individual decides to love the world and its many lusts; that individual will then have decided to not earnestly leave their sins to be closer to God.

God knew precisely what whould happen from the beginning that the jews would reject His salvation and that He would offer it to us gentiles.

We are changed when we make our minds over, by reading the word of God and agreeing with what He says. If we agree with what God says then we will walk it out. Sometings are easier to do than others, but at least out of respect for God we can try. We will have both successes and failures. Thats why its grace that save us and not works, because we arent perfect. But we cant continue in sin or ignore God's instructions to make grace abound.

John the Baptist and the forerunner of Christ and His Kingdom prepares the Jews for the real baptism. I don't believe that he just woke up one day and said to himself 'what if I poured water over people's heads?', instead, he was a vessel of God ever since he was in his mother's womb, lived a holy life and new how to discern the will (and holy whisper) of God...and that's how he came up with water baptism. Water, as shown throughout the Bible, bore a powerful meaning (see Genesis, where the Spirit of God is floating over the face of waters, see the flood, the crossing of the red sea, the water of Bethesda...).

John the Baptist is acting according to his faith, his strong belief that the kingdom of God is at hand

That's a great point. Never heard that idea before, but I'll admit the idea that John would suffer that kind of doubt always seemed strange to me.

I think you are stating a biblical truth, not only about baptism but about the forgiveness of our sins offered by Christ.

Salvation is being born again of the blood of Jesus. Jesus' Atonement transcends time itself because Jesus is God. The OT gives vivid descriptions of the Atonement. It was and is for all time, and water baptism is just a ritualistic remembrance of the true Baptism that takes place the moment we first believe.

The foretelling of all in the OT...

Isaiah
53:1 Who hath believed our report? and to whom is the arm of the LORD revealed?
53:2 For he shall grow up before him as a tender plant, and as a root out of a dry ground: he hath no form nor comeliness; and when we shall see him, [there is] no beauty that we should desire him.
53:3 He is despised and rejected of men; a man of sorrows, and acquainted with grief: and we hid as it were [our] faces from him; he was despised, and we esteemed him not.
53:4 Surely he hath borne our griefs, and carried our sorrows: yet we did esteem him stricken, smitten of God, and afflicted.
53:5 But he [was] wounded for our transgressions, [he was] bruised for our iniquities: the chastisement of our peace [was] upon him; and with his stripes we are healed.
53:6 All we like sheep have gone astray; we have turned every one to his own way; and the LORD hath laid on him the iniquity of us all.
53:7 He was oppressed, and he was afflicted, yet he opened not his mouth: he is brought as a lamb to the slaughter, and as a sheep before her shearers is dumb, so he openeth not his mouth.
53:8 He was taken from prison and from judgment: and who shall declare his generation? for he was cut off out of the land of the living: for the transgression of my people was he stricken.
53:9 And he made his grave with the wicked, and with the rich in his death; because he had done no violence, neither [was any] deceit in his mouth.
53:10 Yet it pleased the LORD to bruise him; he hath put [him] to grief: when thou shalt make his soul an offering for sin, he shall see [his] seed, he shall prolong [his] days, and the pleasure of the LORD shall prosper in his hand.
53:11 He shall see of the travail of his soul, [and] shall be satisfied: by his knowledge shall my righteous servant justify many; for he shall bear their iniquities.
53:12 Therefore will I divide him [a portion] with the great, and he shall divide the spoil with the strong; because he hath poured out his soul unto death: and he was numbered with the transgressors; and he bare the sin of many, and made intercession for the transgressors.

True, but I am saying you were mistaken to think it began at Matthew 28.

Israel was still God's favored nation then.

What is faith in the Lord? Can it be true faith but not faith in what the Lord tells us to do?

Can we say no Lord, I won't be baptized, I have no faith in it, but forgive my sins because I have faith in you? Or are we baptized through our faith in the salvation Christ offers us? I truly do not know the answer to these questions.

For us who are saved after the fall of Israel (Romans 11:11), faith is apart from works of any kind (Romans 4:5).

I don't see how you can say that and believe scripture is truth. Works simply do not work for our salvation, but scripture after scripture speaks of the saved person needing to be a repentant person. You can not be against works having anything to do with salvation when if you are repentant, if you hate sin as we are asked to do, it is impossible not to work to live as a redeemed person.

If works have anything to do with salvation for the Body of Christ, then Romans 4:5 would not make sense.

If in your mind you can only relate works as it applies to working for salvation, then your mind is shutting out works for the love of the Lord and with your limited definition of works, you are correct.