When is “that day”? It is when the ascended Lord makes you one with the Father. “In that day” you will be one with the Father just as Jesus is, and He said, “In that day you will ask Me nothing.” Until the resurrection life of Jesus is fully exhibited in you, you have questions about many things. Then after a while you find that all your questions are gone— you don’t seem to have any left to ask. You have come to the point of total reliance on the resurrection life of Jesus, which brings you into complete oneness with the purpose of God. Are you living that life now? If not, why aren’t you?

“In that day” there may be any number of things still hidden to your understanding, but they will not come between your heart and God. “In that day you will ask Me nothing”— you will not need to ask, because you will be certain that God will reveal things in accordance with His will. The faith and peace of John 14:1 has become the real attitude of your heart, and there are no more questions to be asked. If anything is a mystery to you and is coming between you and God, never look for the explanation in your mind, but look for it in your spirit, your true inner nature— that is where the problem is. Once your inner spiritual nature is willing to submit to the life of Jesus, your understanding will be perfectly clear, and you will come to the place where there is no distance between the Father and you, His child, because the Lord has made you one. “In that day you will ask Me nothing.”

Wisdom from Oswald

The great word of Jesus to His disciples is Abandon. When God has brought us into the relationship of disciples, we have to venture on His word; trust entirely to Him and watch that when He brings us to the venture, we take it.
Studies in the Sermon on the Mount