What evidence was there, in Old Testament times, that the sacrifices being performed would be realised, actually, in the offering up of a humanity?

The complexity and intricacy of the whole array of sacrifices instituted in the wilderness as the children of Israel were instructed to do so, is , in retrospect, clearly a setting forth of all that Christ suffered, expressed in various ways and by different means. The wave offering, the heave offering, the burnt offering, the sin offering : all demonstrate different aspects of the sufferings and death of Christ at Golgotha. But what is there in the Old Testament writings that would have given someone at that time the prospect to look forward to, that, eventually, in God's own time, they would all be realised in *the offering up of a humanity* ? I say 'offering up of a humanity' as I am being careful in the way I express the matter of the humanity and the Deity of Jesus Christ, the Son of God and because I am seeking a response on the basis of Trinitarian Protestantism.