Full Idea
Belief consists merely in a certain feeling or sentiment; in something, that depends not on the will, but must arise from certain determinate causes and principles, of which we are not master.
Gist of Idea
Belief is a feeling, independent of the will, which arises from uncontrolled and unknown causes
Source
David Hume (Treatise of Human Nature, + Appendix [1740], Appen p.2)
Book Reference
Hume,David: 'A Treatise of Human Nature', ed/tr. Selby-Bigge/Nidditch [OUP 1978], p.624
A Reaction
This is the opposite of Descartes' 'doxastic voluntarism' (i.e. we choose what to believe). If you want to become a Christian, steep yourself in religious literature, and the company of religious people. It will probably work.