"As God the everlasting one hath given me a commission to preach his gospel, I command you to believe in the Lord Jesus Christ; not on my own authority, but on the authority of him who said, 'Go ye into all the world and preach the gospel to every creature;' and then annexed this solemn sanction, 'He that believeth and is baptized shall be saved, but he that believeth not shall be damned.' Reject my message, and remember 'He that despised Moses's law, died without mercy under two or three witnesses: of how much sorer punishment, suppose ye, shall he be thought worthy, who hath trodden under foot the Son of God."- From Spurgeon's Sermon Compel Them to Come In
Further recommended reading & listening:
The Best of The Daily Spurgeon
The Forgotten Spurgeon, by Iain Murray