‘And the birds of prey descended on the carcasses, but he drove them away.'
This totally unnecessary description of a seemingly irrelevant incidence is an evidence of the fact that this account came from an eyewitness. Yet it has in it the seed of truth. For the birds of prey are a reminder of those who will seek to prevent his descendants' possession of the land, who as it were are even now trying to prevent the establishing of the covenant, and a reminder that they too can be driven away. It also draws attention to the awfulness of the fates of the victims, not only dead but, were it not for the intervention of the prophet, to be torn up and eaten.
Are we also to see in this incident the sinister figure that lay behind the snake in the Garden of Eden seeking to intervene? He too desires to prevent the establishing of the covenant, for he senses its importance.
But we may ask, what is the purpose of all this? The answer is that it is following ancient custom in the swearing of a solemn oath and the establishing of a solemn covenant (see Jeremiah 34:18-19). The divided animals are saying, ‘let me die if I break this covenant' (Jeremiah 34:20).
But we know that the animals are but a symbol, a type, for the blood that must be shed, for the fulfilment of God's covenant is to be His own blood, shed for the sins of the world.