23 And in that day you will not ask Me for anything. In all sincerity I tell you that whatever you ask the Father in My name He will give it to you.
(alternative reading: whatever you ask the Father, He will give it to you in My name)
24 Up until now you have not asked for anything in My Name. Ask, and you will receive, so that your joy may be completely full.
Whilst we are growing up most of what we need we have to ask our parents for. As children we do not have the means to buy things for ourselves, but gradually parents trust their children with certain amounts of money to go and buy things. This tends to increase as children grow older, until they are able to go and ask for what they need.
Eventually we are able to do this on our own, without the aid of parents.
Jesus told His disciples that they were approaching a time when they would no longer ask Him for anything. What time was Jesus referring to? It would have been the time when the Holy Spirit would be given to them.
He is the One who inspires us as to how we should pray, and what we should pray for.
Perhaps Jesus hinted at this when, earlier in His ministry He said:
Therefore, I say to you that whatever you pray and ask for, you must believe that you have received it and it shall be yours – Mark 11.24.
There was also another occasion when Jesus told His disciples:
 “Keep on asking, and you will be given what you ask for. Keep on looking, and you will find. Keep on knocking, and the door will be opened.
 For everyone who asks, receives. Everyone who seeks, finds. And the door is opened to everyone who knocks – Matthew 7.7-8 (NLT).
Not only does the Holy Spirit prompt us in our praying, He is also our teacher, revealing things to us that we would not otherwise know.
The disciples had been with Jesus for three years. If there was anything that they wanted explaining they were able to go to Jesus and ask Him. That time was coming to a close. However, with the coming of the Holy Spirit they would have Him to teach them and reveal things to them.
We are in the same position. With the presence of the Holy Spirit within us we have the greatest teacher that is possible to have, and the greatest revealer of the mysteries of Jesus.