Actually, no, God certainly knew that man is unable to keep the law perfectly because in the NT we are told that if you keep the whole law but offend in one part, you are guilty of the whole law. That is why the high priest made the sin-offering for the people once a year in the Holy of Holies. That is why Jesus rebuked the Pharisees who boasted that they had kept the entire law when he showed them that God meant not only the letter of the law but the spirit as well. It was not enough to say, "I never killed anyone.", if you had ever hated anyone. It was not enough to say, "I have never committed adultery.", if you had ever lusted after someone not your spouse.
Like Scripture says, the law was made to show us point-blank how sinful we really are and how we all, no matter how good we think we are, need a savior. Besides, do you really think the perfection of God, the holiness of God is attainable by man alone? We sin before we are even old enough to know that is what we are doing.
We are all sinners and if Christ had never come for us, we would all be rightfully condemned to eternal separation from God. But God, in his infinite mercy and grace did not leave us in this state. He came to earth as a man, lived that perfect life, and willingly gave that life as a sacrifice, a propitiation, for our sins. It satisfied his demand for justice, his insistence on holiness and perfection and his command that "without the shedding of blood, there can be no remission of sins.".
Isn't that convenient? :) Yet there is nothing in the Five Books of Moses to suggest God gave Moses his eternal Law to show Moses and the Hebrews the need for a Christ-like savior. The OT God calls himself the savior of his people because that's what he did: he took them out of bondage and gave them a promised land.
In return he demanded that people obey his Law forever, and worship only him. And if they didn't, he unleashed all sorts of evil on them, Zeus style. The OT God demanded obedience and he was loving to those who obeyed him and terrible to those who didn't. No need for another savior.
That is why the high priest made the sin-offering for the people once a year in the Holy of Holies
And the OT says that was acceptable to God, and is in fact part of the eternal Torah, the 613 mitzvot, which is to be observed forever, which God wrote before the foundation of the world (according to mishnah).
And the OT God gave the seven Noachide Laws for the Gentiles and that is the only thing the Gentiles need (according to the OT). They are not and never have been under the Law. But at the same time, the seven laws given were sufficient for the Gentles, and no additional "salvation" or savior is called for in the Torah.
Like Scripture says, the law was made to show us point-blank how sinful we really are
We are sinful by design, or else God is not in control.
Besides, do you really think the perfection of God, the holiness of God is attainable by man alone?
Man was not created to be divine, so why should he be perfect (holy)?
We are all sinners and if Christ had never come for us, we would all be rightfully condemned to eternal separation from God
By design.
He came to earth as a man, lived that perfect life, and willingly gave that life as a sacrifice, a propitiation, for our sins. It satisfied his demand for justice, his insistence on holiness and perfection and his command that "without the shedding of blood, there can be no remission of sins."
An innocent man dying for the sins of the world is not justice but injustice no matter how you turn it around. And if God insisted on holiness and perfection of man, why didn't he just make man holy and perfect, and the world eternally blissful, and spared himself and the world all the blood, guts, holocausts and suffering?