en_tn_lite_do_not_use/mrk/11/23.md

Truly I say to you

"I tell you the truth." This phrase adds emphasis to what Jesus says next.

if he does not doubt in his heart but believes

Here "heart" is a metonym for a person's mind or inner being. Alternate translation: "if he truly believes in his heart" or "if he does not doubt but believes" (See: rc://en/ta/man/jit/figs-metonymy)

God will do

"God will make happen"