18 Now in the morning, as He returned to the city, He was hungry. 19 And seeing a fig tree by the road, He came to it and found nothing on it but leaves, and said to it, “Let no fruit grow on you ever again.” Immediately the fig tree withered away.
20 And when the disciples saw it, they marveled, saying, “How did the fig tree wither away so soon?”
21 So Jesus answered and said to them, “Assuredly, I say to you, if you have faith and do not doubt, you will not only do what was done to the fig tree, but also if you say to this mountain, ‘Be removed and be cast into the sea,’ it will be done. 22 And whatever things you ask in prayer, believing, you will receive.”
23 Now when He came into the temple, the chief priests and the elders of the people confronted Him as He was teaching, and said, “By what authority are You doing these things? And who gave You this authority?”
24 But Jesus answered and said to them, “I also will ask you one thing, which if you tell Me, I likewise will tell you by what authority I do these things: 25 The baptism of John—where was it from? From heaven or from men?”
And they reasoned among themselves, saying, “If we say, ‘From heaven,’ He will say to us, ‘Why then did you not believe him?’ 26 But if we say, ‘From men,’ we fear the multitude, for all count John as a prophet.” 27 So they answered Jesus and said, “We do not know.”
And He said to them, “Neither will I tell you by what authority I do these things.
28 “But what do you think? A man had two sons, and he came to the first and said, ‘Son, go, work today in my vineyard.’ 29 He answered and said, ‘I will not,’ but afterward he regretted it and went. 30 Then he came to the second and said likewise. And he answered and said, ‘I go, sir,’ but he did not go. 31 Which of the two did the will of his father?”
They said to Him, “The first.”
Jesus said to them, “Assuredly, I say to you that tax collectors and harlots enter the kingdom of God before you. 32 For John came to you in the way of righteousness, and you did not believe him; but tax collectors and harlots believed him; and when you saw it, you did not afterward relent and believe him.Matthew 21:18-32 (NKJV)
Jesus curses the fig tree in 18-19. The lesson of it is in 20-22. The “faith” in 21 presupposes that whatever is being requested is in God’s will.
The chief priests and elders try to trap Jesus with their question (23). Jesus catches them in their own trap (24-27).
28-32 tells a parable of the two sons. It has nothing to do with money. Instead, it is a parable on belief. Jesus is still speaking to the same people from 23. Believing in God is to do the will/works of God (see John 6:29 in context of John 6:22-71).