Hebrews 11 and Alma 32. Both of these passages provide us with the basic principle of faith. Alma 32:21 says that faith is "not to have a perfect knowledge of things," but to "hope for things which are not seen, which are true." At first, this idea of hoping for things we can't see is pretty abstract and hard to understand. But I like how Alma further explains this and compares the idea of faith to a seed so even a child can understand it. The LDS Children's song book provides a great song on faith that explains it well:
Faith is knowing the sun will rise, lighting each new day.
Faith is knowing the Lord will hear my prayers each time I pray.
Faith is a swelling within my heart. When I do right, I know.
Faith is trust in God above; In Christ, who showed the way.
Faith is strengthened; I feel it grow Whenever I obey.
Hebrews 11 states that "faith is the substance of things hoped for, the evidence of things not seen." Faith in the Lord Jesus Christ and His Atonement is central to our beliefs as members of the Church of Jesus Christ of Latter-Day Saints. I've never seen Christ, but I have a deep faith that He lives and loves me. I know that following His teachings will bring us greater happiness in this life and in the life to come. May we all continue to live His teachings and "choose to suffer affliction with the people of God, rather than to enjoy the pleasures of sin for a season." Hebrews 11:25