Why does one of God’s ministers preach the gospel powerfully? Because God gives him assistance. Why does Joseph stand against temptation? Because God gives him aid. The strength of a Christian is divine strength. My brethren, I am more and more persuaded every day that the sinner has no power of himself, except that which is given him from above. I know that if I were to stand with my foot upon the golden threshold of heaven’s portal, if I could put this thumb upon the latch, I could not open that door, after having gone so far towards heaven, unless I had still supernatural power communicated to me in that moment. If I had a stone to lift, to work my own salvation, without God’s help to do that, I must be lost, even though it were so little. There is naught that we can do without the power of God. All true strength is divine. As the light cometh from the sun, as the shower from heaven; so doth spiritual strength come from the Father lights, with whom there is neither variableness nor shadow of a turning.
From the Metropolitan Tabernacle Pulpit, Volume 1, Sermon 17 by Charles Haddon Spurgeon