The below titled link is from Rapture Ready and I found it to be a wonderful explanation of the faith, belief, obedience and salvation of the Old Testament Saints (ie. Abraham, Sarah, Noah, Moses, David, Isaiah, etc.). After our Lord Jesus Christ died on the cross and was buried/placed in the tomb for 3-days, He did not arise and arrive alone, no, He brought with Him all the Saints of The Old Testament. It is recorded FACT that for the 40-day time period Jesus walked throughout Jerusalem, so did thousands of “believers” who had actually died/passed and gone on before Him.
During the Resurrection period, Jesus Christ, The Messiah who was born into this world and came as God Himself to reconcile God The Father’s Creation (Man) back to Him by sacrificing His Pure Blood and His sinless earthly life, He went below to the underbelly of the earth to a place called Sheol, a place God The Father had secured for His precious faithful servants/children who had lived and served Him prior to the death of Jesus. Why were these Old Testament Saints not already sitting pretty in Heaven, in a place God had already prepared for them? Heaven was not open until the birth and death of Jesus – He held the Keys to an Open Heaven and since sin was not allowed to reach God’s Holy Mansion/Home or even the Holy Grounds upon which this all sat upon, they too could not step foot there until His Perfect Sacrifice was made, cleansing the sins of those too who died before Him. Jesus now could unlock a closed Heaven and allow His Grace and Divine Covering over those Children of God too. (See below link) No one, not one soul could enter God’s Holy Presence until the “cleansing of their earthly sins” and that could not happen until Jesus’ death on the cross at Golgotha. He went below, unlocked and removed the chains of death for He had the Keys to death and through Him, they that were there could follow Him out and move on to the place now available to all who accepted Him as their Savior – to all who “knew” Him and would come to know Him. Jesus held the Key to Heaven, an “open door” was now allowing God to fulfill His Promises to His Children. Remember too that at this time, Jesus the Messiah, the Savior, shown Himself and His Godhead to the other’s who were on the “hell” or “evil” side of the underbelly and gave them too the chance to accept Him and to believe that He was The Son of God who had indeed came as God in the flesh and through Him, they too could receive everlasting life with The Father in Heaven if they repented of their sins and asked Him for forgiveness. Just as it will be again in the not-to-distant-future, some accepted this gift but most who were there, did not. He gave them a chance – don’t ever think He didn’t try to give them “their second chance” because He did.