vi. 8. _Then said I, Here am I, send me._ This is a chapter of autobiography. Here is disclosed the secret of the wonderful energy with which for more than half a century Isaiah prosecuted his ministry. He is the Paul of the Old Testament. Allowance being made for difference of phraseology, there is a striking resemblance between the call of Isaiah and of Paul (comp. chap. vi. with Acts ix.). Both sought to serve the heavenly King; and both received a commission to work, spiritual and catholic beyond all conceptions of their time,--the one penning the Gospel of the suffering Messiah, the other vindicating the truth that the Gospel is God's message to the _world._ The text reminds us-- +I. Of the Christian's offer of service.+ The offer of service which the prophet made was--1. _Free._ He spoke spontaneously, and not as the result of pressure from without.[1] 2. _Truthful._ Unlike one of the sons in the parable (Matt. xxi. 30), he meant what he said. 3. _Bold._ It was made concerning an unknown mission. The justification of the boldness of his offer is, that it was made to God, who always qualifies His servants for the tasks to which He calls them. 4. _Personal._ The prophet placed at God's disposal, not some of his property merely, but _himself._ 5. _It involved the most complete self-surrender._ All thought of self control the prophet resigned. He placed himself as an instrument in God's hands. He was ready go to where, when, and on what errand God might determine.[2] Such are the offers of service in which God delights. +II. Of the steps that lead up to this offer.+ The offer may take men by surprise, but there has always been preparation for it, as there has been long preparation for the lightning that leaps suddenly from the sky. Such offers as the prophet made are preceded--1. By _a vision of God,_ of the thrice Holy One, filling the soul with awe, and causing it to tremble (vers. 1-4). 2. By _self-prostration of spirit,_ a conviction of utter sinfulness (ver. 5). This is the invariable result of a true vision of God (Exod. iii. 2; Josh. v. 14; Judg. vi. 22, xii. 22; Luke v. 8; Rev. i. 17). This is also a prime condition of fitness for service. 3. By _the touch of a mediator_ (vers. 6, 7). "They that be struck down by visions of God's glory shall soon be raised up again by visits of His grace." Blessed is the man who has _both_ visions. A sense of pardon is essential to large usefulness. Imperfect realisation of forgiveness is one of the most frequent causes of weakness in Christian service. 4. By _a moral transformation._ The offerer has become a new man from the centre outwards. Now he can hear God's voice: "I heard," &c. It is a voice to which now he feels he _must_ respond: "Here am I," &c. In some degree every Christian is thus prepared. These essentials of service are also essentials of Christian life. These experiences are at once your credentials and your powers.