Rom 4:20-25, Jn 8:56, Lk 24:25-27
Heb 11:17 By faith Abraham, when he was tried, offered up Isaac: and he that had received the promises offered up his only begotten son, 18 Of whom it was said, That in Isaac shall thy seed be called: 19 Accounting that God was able to raise him up, even from the dead; from whence also he received him in a figure.
When Abraham offered Isaac as a sacrifice, he believed that God would raise Isaac back because of Christ, who would come as a descendant of Isaac. In other words, Abraham believed in the coming Christ. God counted those who believed in Jesus Christ as righteousness just as he counted Abraham's faith as righteousness. (Rom 4:20-25, Jn 8:56)
Rom 4:20 He staggered not at the promise of God through unbelief; but was strong in faith, giving glory to God; 21 And being fully persuaded that, what he had promised, he was able also to perform. 22 And therefore it was imputed to him for righteousness. 23 Now it was not written for his sake alone, that it was imputed to him; 24 But for us also, to whom it shall be imputed, if we believe on him that raised up Jesus our Lord from the dead; 25 Who was delivered for our offences, and was raised again for our justification.
Jn 8:56 Your father Abraham rejoiced to see my day: and he saw it, and was glad.
After all, the Old Testament describes Christ and prophesied that Christ would come. That Christ is Jesus. (Lk 24:25-27)
Lk 24:25 Then he said unto them, O fools, and slow of heart to believe all that the prophets have spoken: 26 Ought not Christ to have suffered these things, and to enter into his glory? 27 And beginning at Moses and all the prophets, he expounded unto them in all the scriptures the things concerning himself.