Mark 11:24

This verse is quoted more often outside its context than in it, and the context does most of the interpretive work.

It is said the morning after Jesus cursed a fig tree and cleared the temple. Peter points out the withered tree; this is the answer. So the mountain-moving language a verse earlier and this promise are both spoken in the shadow of a judgment on fruitlessness and on a temple that had become a market.

And the very next verse attaches a condition that is almost never quoted alongside: whenever you stand praying, forgive, if you have anything against anyone. Jesus follows the largest promise about prayer in the Gospels with a requirement about your relationships. The two are one instruction.

That placement rules out the reading this verse usually gets — a technique for obtaining outcomes by sufficiently confident believing. The belief in question is not self-generated certainty about a result. In Mark's arrangement it sits between a judgment on religion that had stopped bearing fruit and a command about forgiveness.

Believe that you have received them is in a tense suggesting something already completed. Which is worth noticing: the confidence described is not about the future arriving as ordered. It is about something already settled elsewhere.