1. He who is God’s incarnation shall hold the substance of God, and He who is God’s incarnation shall hold the expression of God. Since God becomes flesh, He shall bring forth the work He must do, and since God becomes flesh, He shall express what He is, and shall be able to bring the truth to man, bestow life upon man, and show man the way. Flesh that does not contain the substance of God is surely not the incarnate God; of this there is no doubt, of this there is no doubt.
2. To investigate whether it is God’s incarnate flesh, whether it is God’s incarnate flesh, man must determine this from the disposition He expresses and the words He speaks. Whether or not it is God’s incarnate flesh, and whether or not it is the true way, must be judged from His substance. And so, in determining whether it is the flesh of God incarnate, the key is to pay attention to His substance (His work, His words, His disposition, and many more), rather than external appearance. The key is to pay attention to His substance, rather than external appearance.
from Preface to The Word Appears in the Flesh