There is a question about greatness in heaven. Jesus does not say “the first shall be last and the last shall be first” at this time but that idea is present in his answer about humility and forgiveness.

Matthew 18

At that time the disciples came to Jesus saying “Who is the greatest in the kingdom of heaven?”

2 Jesus called a little child to him, and placed him in the midst of them,

3 And said “Truly I say to you, Except you be converted, and become as little children, you shall not enter into the kingdom of heaven.

4 Whoever humbles himself as this little child, the same is greatest in the kingdom of heaven.

5 And whoever receives one such little child in my name receives me.

6 But whoever causes one of these little ones who believe in me to sin, it would be better to have a millstone hung around his neck and be drowned in the depth of the sea.

7 Woe to the world because of temptations to sin! For it is necessary that temptations come, but woe to that man by whom the temptations come!

8 Therefore if your hand or your foot offend thee, cut them off, and cast them from you. It is better for you to enter into life crippled or lame than having two hands or two feet to be cast into everlasting fire.

9 If your eye offends you, pluck it out and cast it from you. It is better for you to enter into life with one eye than having two eyes to be cast into hell fire.

10 Be careful that you do not despise one of these little ones; for I say to you that in heaven their angels do always see the face of my Father who is in heaven.

11 For the Son of man is come to save that which was lost.

12 What do you think? If a man has a hundred sheep, and one of them goes astray, does he not leave the ninety nine, and go into the mountains to seek that which has gone astray?

13 And if he finds it, truly I say to you, he rejoices more over that sheep than the ninety  nine which did not stray.

14 Even so it is not the will of your Father in heaven that one of these little ones should perish.

15 If your brother sins against you, go and tell him his fault between you and him alone: if he will hear you, you have gained your brother.

16 But if he will not hear you, then take with you one or two more, so that in the testimony of two or three witnesses every word may be established.

17 If he refuses to hear them, tell the church: and if he refuses to hear the church, let him be to you as an unbeliever and a tax collector. 

18 Truly I say to you, Whatever you bind on earth will be bound in heaven and whatever you loose on earth will be loosed in heaven.

19 Again I say to you, That if two of you shall agree on earth on anything in prayer, it shall be done for them by my Father who is in heaven.

20 For where two or three are gathered together in my name, there I am in the midst of them.”

21 Then Peter came to him and said “Lord, how many times shall my brother sin against me, and I forgive him? Up to seven times?”

22 Jesus said to him “I do not say up to seven times: but, seventy times seven.

23 The kingdom of heaven is like a certain king who wanted to settle accounts with his servants.

24 And when he began to settle accounts, one was brought to him which owed him ten thousand talents.

25 But since he had no way to pay, his lord commanded him to be sold, and his wife, and children, and all that he had, and payment to be made.

26 Therefore the servant fell down, and worshiped him, saying ‘Lord, have patience with me and I will pay you everything.’

27 Then the lord of that servant was moved with compassion, and set him free, and forgave him the debt.

28 But the same servant went out and found one of his fellow servants, which owed him a hundred pence: and he laid hands on him, and took him by the throat, saying ‘Pay me what you owe.’

29 His fellow servant fell down at his feet and begged him, saying ‘Have patience with me and I will pay you all that I owe.’

30 And he refused and had him cast into prison, till he should pay the debt.

31 So when the other servants saw what was done, they were distressed and came and told their lord all that was done.

32 Then his lord, after that he summoned him, said to him ‘O you wicked servant, I forgave you all that debt because you pleaded with me.

33 Should you not also have had mercy on your fellow servant, even as I had mercy on you?’

34 His lord was very angry, and delivered him to the jailers to be tortured until he should repay all that was due him.

35 My heavenly Father shall do the same to you also, if you do not forgive from your hears every one of your brothers trespasses.”

Compare and contrast: Matthew 18 in ESV, HCSB, NASB, NIV via Bible Gateway.