Why was it necessary for Christ to humble Himself even to death?
Because with regard to the justice and truth of God, satisfaction for our sins could be made only by the death of the Son of God.
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Why was He also buried?
To prove that He was really dead.
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Since then Christ died for us, why must we also die?
Our death is not a satisfaction for our sins, but only an abolishing of sin and a passage into eternal life.
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What further benefit do we receive from the sacrifice and death of Christ on the cross?
That by virtue of it our old self is crucified, dead, and buried with Him, that so the corrupt inclinations of the flesh may no more reign in us, but that we may offer ourselves to Him a sacrifice of thanksgiving.
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Why is there added: He descended into hell?
That in my greatest temptations I may be assured and wholly comfort myself in this, that my Lord Jesus Christ, by His inexpressible anguish, pains, terrors, and hellish agonies in which He was plunged during all His sufferings, but especially on the cross, has delivered me from the anguish and torments of hell.