This Jesus saying about faith and prayer can also be found in Matthew, chapter 21:22, sometimes word for word. Mark indicated that Jesus told his disciples (διὰ τοῦτο λέγω ὑμῖν) that whatever they asked for in prayer (πάντα ὅσα προσεύχεσθε καὶ αἰτεῖσθε), they would receive it or it would be theirs (καὶ ἔσται ὑμῖν). If they believed (πιστεύετε), they would receive it (ὅτι ἐλάβετε), it would happen. The essential ingredient of effective prayer was faith.
καὶ πάντα ὅσα ἂν αἰτήσητε ἐν τῇ προσευχῇ πιστεύοντες λήμψεσθε.
This Jesus saying about faith can be found in Mark, chapter 11:20-24, word for word, but it was the next day after the curse, not the same day. Jesus answered the disciple’s question (ἀποκριθεὶς δὲ ὁ Ἰησοῦς εἶπεν αὐτοῖς) about how the fig tree withered with a solemn pronouncement (Ἀμὴν λέγω ὑμῖν) about the importance of faith. If they had faith (ἐὰν ἔχητε πίστιν) and did not doubt (καὶ μὴ διακριθῆτε), they too would be able to effectively curse a fig tree (οὐ μόνον τὸ τῆς συκῆς ποιήσετε). Not only that, but if they had faith, they could move mountains. They could tell a mountain (ἀλλὰ κἂν τῷ ὄρει τούτῳ εἴπητε) to be lifted up or taken away (Ἄρθητι) and thrown into the sea (καὶ βλήθητι εἰς τὴν θάλασσαν), and it would happen (γενήσεται). Whatever they asked for in believing prayer (καὶ πάντα ὅσα ἂν αἰτήσητε ἐν τῇ προσευχῇ πιστεύοντες), they would receive it (λήμψεσθε). The essential ingredient of effective prayer was faith.