Calvin: "...Luke wanted to show that Peter was strong only because he was filled with the Holy Spirit," (Sermons on Acts, p.129). Standing before the mighty Jewish Sanhedrin accused of the healing of the lame man, Peter and John made their defence statement. That statement was a reaffirmation of the fact that it was Jesus of Nazareth, Whom they crucified, who raised this lame man to full physical agility, not them. They gave Jesus all the credit and glory for this mighty act of healing.
But what empowered Peter to speak like this, being an ignorant and uneducated man, was his being "filled with the Holy Spirit." This is not the first time Peter experienced this infilling of the Spirit. It happened before on the Day of Pentecost when God poured out His Spirit on the apostle's preaching. Peter was filled with the Holy Spirit. But this was not the last time this happened to the apostle. Every time he had something significant to do for Christ, he was endued with "power from on high." When the groups of believers were met together after Peter and John had been released from the 71-strong Sanhedrin, they prayed to the sovereign Lord and were all filled with the Holy Spirit, Peter included (Acts 4:31).
Calvin is correct: we are weak and inform when we are deprived of Him.
But there is much more to this than just help when we need it. This is a special filling for a special purpose. And it is this that preachers need more than anything else today. We have all our theology and correct doctrine; but we do not have the Spirit in power. We can preach well-constructed sermons, but have no power. We can woo congregations with our weepy concluding stories, but no power. It is power we need, power to live, power to preach, and power to witness to Christ in every situation. Without this heavenly enabling, all our preaching and witnessing are in vain.
The preachers of old were men who knew the filling of the Spirit in great measure. Think of men like John and Charles Wesley, George Whitefield, Daniel Rowlands, Jonathan Edwards, R. M. McCheyne, etc. They knew the Spirit's power on their lives and ministries. How we need to know that today.
Let us pray to the sovereign Lord that all Gospel preachers will be Spirit-filled men, and that when they stand up to preach, it will be "in demonstration of the Spirit and of power."