But Paul cried with a loud voice, "Do not harm yourself, for we are all here."
And the jailer called for lights and rushed in, and trembling with fear he fell down before Paul and Silas. Then he brought them out and said, "Sirs, what must I do to be saved?"
And they said, "Believe in the Lord Jesus, and you will be saved, you and your household." And they spoke the word of the Lord to him and to all who were in his house. And he took them the same hour of the night and washed their wounds; and he was baptized at once, he and all his family.
(Acts 16:25-33 ESV)
"If you see it, there is no point in delaying. You say at once, 'I can trust him now as well as tomorrow or in a thousand years time. I believe now.' You will never be any better or any more qualified than you are now. Belief is immediate.
"Believing on the Lord Jesus Christ is accepting his testimony, setting your seal to it that the word is true, saying, 'If I do not believe it I am making him a liar. I do not understand, but I have believed.'"
--Martyn Lloyd-Jones, Experiencing the New Birth (Crossway Books, 2015)