Now in the morning, as they passed by, they saw the fig tree dried up from the roots. And Peter, remembering, said to Him, “Rabbi, look! The fig tree which You cursed has withered away.” So Jesus answered and said to them, “Have faith in God. For assuredly, I say to you, whoever says to this mountain, ‘Be removed and be cast into the sea,’ and does not doubt in his heart, but believes that those things he says will be done, he will have whatever he says. Therefore I say to you, whatever things you ask when you pray, believe that you receive them, and you will have them.
— Mark 11:20-26
Truly I tell you, if you have faith as small as a mustard seed, you can say to this mountain...
— Matt 17:20
Faith is the substance of things hoped for...
— Hebrews 11:1
So Jesus answered and said to them, “Have faith in God. For assuredly, I say to you, whoever says to this mountain...
— Mark 11:22
“With men this is impossible, but with God all things are possible.”
— Matt 19:26
Why do you need Faith? Well, it is strong enough to confront the brutal facts, optimism isn't. Optimism tries to ignore them, even pretend that they don't exist. But faith doesn't get derailed by the facts. It is strong enough and secure enough to confront them and deal with them.
— Matt Edmundson