Seeing then that we have a great High Priest, that is passed into the heavens, Jesus the Son of God, let us hold fast our profession. – Hebrews 4:14

As prayer will not be truly prayer without the Spirit of God, so it will not be prevailing prayer without the Son of God. He, the great High Priest, must go within the veil for us; nay, through His crucified person the veil must be entirely taken away; for, until then, we are shut out from the living God. The man who, despite the teaching of Scripture, tries to pray without a Saviour insults the Deity; and he who imagines that his own natural desires, coming up before God, unsprinkled with the precious blood, will be an acceptable sacrifice before God, makes a mistake; he has not brought an offering that God can accept, any more than if he had offered an unclean sacrifice. Wrought in us by the Spirit, presented for us by the Christ of God, prayer becomes power before the Most High, but not else.

Now, let us continue in prayer, yea, let us gather strength in intercession, and the more we succeed, the more earnest let us be to succeed yet more and more. Let us not be straitened in our own bowels, since we are not straitened in our God. This is a good day, and a time of glad tidings, and seeing that we have the King’s ear, I am most anxious that we should speak to Him for thousands of others; that they also, in answer to our pleadings, may be brought nigh unto Christ. ~ C.H. Spurgeon

https://www.blueletterbible.org/Comm/spurgeon_charles/sermons/1024.cfm