Charles H. Spurgeon on Psalms 105:9

Which covenant he made with Abraham. When the victims were divided and the burning lamp passed between the pieces (Gen. 15.) then the Lord made, or ratified, the covenant with the patriarch. This was a solemn deed, performed not without blood, and the cutting in pieces of the sacrifice; it points us to the greater covenant which in Christ Jesus is signed, sealed, and ratified, that it may stand fast for ever and ever. And his oath unto Isaac. Isaac did not in vision see the solemn making of the covenant, but the Lord renewed unto him his oath (Ge 26:2-5). This was enough for him, and must have established his faith in the Most High. We have the privilege of seeing in our Lord Jesus both the sacrificial seal, and the eternal oath of God, by which every promise of the covenant is made yea and amen to all the chosen seed.