God and Christ knew from the beginning, of the apostasy of Satan and of the fall of Adam through the deceptive power of the apostate. The plan of salvation was designed to redeem the fallen race, to give them another trial. Christ was appointed to the office of Mediator from the creation of God, set up from everlasting to be our substitute and surety.—Selected Messages 1:250. TA 24.4
Known unto God are all His works, and from eternal ages the covenant of grace (unmerited favor) existed in the mind of God. It is called the everlasting covenant; for the plan of salvation was not conceived after the fall of man, but it was that which was “kept in silence through times eternal, but now is manifested, and by the Scriptures of the prophets, according to the commandment of the eternal God, is made known unto all the nations unto obedience of faith.” Romans 16:25, 26, A.R.V.—The Signs of the Times, December 15, 1914. TA 25.1
The plan for our redemption was not an afterthought, a plan formulated after the fall of Adam. It was a revelation of “the mystery which hath been kept in silence through times eternal.” Romans 16:25, R.V. It was an unfolding of the principles that from eternal ages have been the foundation of God's throne.... God did not ordain that sin should exist, but He foresaw its existence, and made provision to meet the terrible emergency.—The Desire of Ages, 22. TA 25.2