When we speak of a call we nearly always leave out one essential feature, viz.: the nature of the one who calls. We speak of the call of the sea, the call of the mountains, the call of the great ice barriers. These calls are heard by a few only because the call is the expression of the nature from which the call comes, and can only be heard by those who are attuned to that nature.
The call of God is essentially expressive of the nature of God, it is His own voice. Paul says that “God commendeth His own love toward us” (rv). the love that is exactly expressive of His nature. Get that thought with regard to the call of God. Very few of us hear the call of God because we are not in the place to answer; the call does not communicate because we have not the nature of the One Who is calling. In the case of Isaiah, his soul was so attuned because of the tremendous crisis he had passed through, that the call of God was recorded to his amazed soul. God did not lay a strong compulsion on Isaiah; Isaiah was in the presence of God and he overheard, as it were, the soliloquy of God: “Whom shall I send, and who will go for Us?” and in conscious freedom he replied, “Here am I; send me.”
There is a good deal of instruction to be got by watching the faces of people in certain surroundings—by the sea shore, in an art gallery, during music; you can tell at once if they are listening to the call of the thing or simply reflecting themselves. Most of us have no ear for anything but ourselves, anything that is not “me” we cannot hear. We are dead to, and without interest in the finest music, we can yawn in a picture gallery, and be uninspired by a sunrise or a sunset. That is true not only of the soul’s denseness to natural beauties, or to music and art and literature, but true with regard to the awakening of the soul to the call of God. To be brought within the zone of God’s voice is to be profoundly altered.