“Jesus answered them.

‘Truly!

I say to you!

If you have faith,

If you do not doubt,

Not only will you do

What has been done

To the fig tree,

But even if you say

To this mountain.

‘Be lifted up!

Be thrown into the sea!’

It will be done.

Whatever you ask for

In prayer,

With faith,

You will receive.’”

ἀποκριθεὶς δὲ ὁ Ἰησοῦς εἶπεν αὐτοῖς Ἀμὴν λέγω ὑμῖν, ἐὰν ἔχητε πίστιν καὶ μὴ διακριθῆτε, οὐ μόνον τὸ τῆς συκῆς ποιήσετε, ἀλλὰ κἂν τῷ ὄρει τούτῳ εἴπητε Ἄρθητι καὶ βλήθητι εἰς τὴν θάλασσαν, γενήσεται·

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.