Just as one who is to be admitted to Judaism must first submit to the three ceremonies of circumcision, baptism, and sacrifice, so Israel did not receive the Torah until they had performed these three ceremonies. They had already undergone circumcision in Egypt. Baptism was imposed upon them two days before the revelation on Mount Sinai. On the day preceding the revelation Moses recorded in a book the covenant between Israel and their God, and on the morning of the day of the revelation, sacrifices were offered as a strengthening of the covenant. 
As there were no priests at that time, the service was performed by the elders of Israel, who in spite of their age performed their duty with youthful vigor.  Moses erected an altar on Mount Sinai, as well as twelve memorial pillars, one for each tribe, and then bade them bring bulls, as a burnt offering and a peace offering.  The blood of these animals was then separated exactly into two halves. This was attended to by the angel Michael, who guided Moses' hand, and so conducted the separation of the blood that there might be not a drop more in one half than in the other. God upon this said to Moses: "Sprinkle the one half of the blood upon the people, as a token that they will not barter My glory for the idols of other peoples; and sprinkle the other half on the altar, as a token that I will not exchange them for any other nation." Moses did as he was bidden, and lo! the miracle came to pass that the blood of a few animals sufficed to sprinkle every single Israelite.
Before this covenant between God and Israel had been made, Moses read aloud to the people all of the Torah, that they might know exactly what they were taking upon themselves. This covenant was made a second time in the desert of Moab by Moses, and a third time by Joshua after the entrance into the promised land, on the mountains of Gerizim and Ebal. 
Although the people had now clearly expressed their desire to accept the Torah, still God hesitated to give it to them, saying: "Shall I without further ado give you the Torah? Nay, bring Me bondsmen, that you will observe it, and I will give you the Torah." Israel: "O Lord of the world! Our fathers are bondsmen for us." God: "Your fathers are My debtors, and therefore not good bondsmen. Abraham said, 'Whereby shall I know it?' and thus proved himself lacking in faith. Isaac loved Esau, whom I hated, and Jacob did not immediately upon his return from Padan-Aram keep his vow that he had made upon his way there. Bring Me good bondsmen and I will give you the Torah." Israel: "Our prophets shall be our bondsmen." God: "I have claims against them, for 'like foxes in the deserts became your prophets.' Bring Me good bondsmen and I will give you the Torah." Israel: "We will give Thee our children as bondsmen." God: "Well, then, these are good bondmen, on whose bond I will give you the Torah." Hereupon the Israelites brought their wives with their babes at their breasts, and their pregnant wives, and God made the bodies of the pregnant women transparent as glass, and He addressed the children in the womb with these words: "Behold, I will give your fathers the Torah. Will you be surety for them that they will observe it?" They answered: "Yea." He furthermore said: "I am your God." They answered: "Yea." "Ye shall have no other gods." They said: "Nay." In this wise the children in the womb answered every commandment with "Yea," and every prohibition with "Nay." As it was the little children upon whose bond God gave His people the Torah, it comes to pass that many little children die when Israel does not observe the Torah.