This constant undivided union of two perfect natures in Christ’s person is exactly that which gives infinite value to His mediation and qualifies Him to be the very Mediator that sinners need.  Our Mediator is one who can sympathize because He is very man.  And yet, at the same time, He is one who can deal with the Father for us on equal terms because He is very God. – J. C. Ryle (1816-1900)

Source: On the Hypostatic Union