"what saith the Lord, what is His word for the people. If they rely upon discourses prepared years before they may fail to meet the necessities of the occasion. Their hearts should be laid open so that the Lord may impress their minds, and then they will be able to give the people the precious truth warm from heaven. God is not pleased with those narrow-minded ministers who devote their God-given powers to matters of little moment and fail to grow in divine knowledge to the full stature of men in Christ Jesus. He would have His ministers possess breadth of mind and true moral courage. Such men will be prepared to meet opposition and surmount difficulties, and will lead the flock of God instead of being led by them. 5T 252.1"
"If any man speak, let him speak as the oracles of God; if any man minister, let him do it as of the ability which God giveth: that God in all things may be glorified through Jesus Christ, to whom be praise and dominion for ever and ever. Amen."
Both passages emphasize the importance of speaking/ministering according to God's word and with the ability that God provides. EGW elaborates on this by discussing the need for ministers to be open to divine inspiration and to grow in divine knowledge.
"There is altogether too little of the Spirit and power of God in the labor of the watchmen. The Spirit which characterized that wonderful meeting on the Day of Pentecost is waiting to manifest its power upon the men who are now standing between the living and the dead as ambassadors for God. The power which stirred the people so mightily in the 1844 movement will again be revealed. The third angel's message will go forth, not in whispered tones, but with a loud voice. 5T 252.2"
"And they were all filled with the Holy Ghost, and began to speak with other tongues, as the Spirit gave them utterance."
EGW draws a parallel between the outpouring of the Holy Spirit at Pentecost and a future outpouring that will empower the third angel's message. The reference to the Spirit and power of God connects directly to the filling of the Holy Ghost in Acts 2:4.
"Many who profess to have great light are walking in sparks of their own kindling. They need to have their lips touched with a live coal from off the altar, that they may pour forth the truth like men who are inspired. Too many go into the desk with mechanical discourses that have no light from heaven in them. 5T 252.3"
"Then flew one of the seraphims unto me, having a live coal in his hand, which he had taken with the tongs from off the altar: And he laid it upon my mouth, and said, Lo, this hath touched thy lips; and thine iniquity is taken away, and thy sin purged."
EGW directly alludes to Isaiah 6:6-7, using the imagery of a live coal from the altar touching the lips to represent purification and empowerment for speaking truth.