23 In that day you will ask nothing of me. Truly, truly, I say to you, whatever you ask of the Father in my name, He will give it to you. 24 Until now you have asked nothing in my name. Ask, and you will receive, that your joy may be full. ~ John 16:23–24
Jesus explains to His disciples that in that day. What day was Jesus referring to? The days after His death, burial, and resurrection. In other words, after He had been glorified and ascended into heaven. In that day, they would have access straight to the Father again, just like Adam and Eve had in the beginning. They would not have to go through a high priest because, at His death, the veil in the Temple was torn in two.
Jesus, Himself, promises that if we ask anything in His name, He will do it for us, and He cannot deny His own words, neither can He neglect His own promises. Not only once but several times, He reiterated the promise showing that it was not a slip of the tongue or a mistake in speaking. It was and is His solemn promise.
Peace. Love. Go Forth and Ask In His Name.