The following is a Greek word commentary, taken from Wuest Word Studies – K. S. Wuest, on Mark 11:22 – 26
Mark 11:22 – Our Lord’s answer to Peter, on the surface so unrelated to Peter’s words, is explained by Swete as follows: “The answer is remarkable; the Lord does not explain the lesson to be learned from the fate of the tree, but deals with a matter of more immediate importance to the Twelve, the lesson to be learned from the prompt fulfillment of His prayer.” This is just another instance in the life of our Lord that brings to view His humanity and His dependence upon God the Holy Spirit, for the words He uttered, the prayers which He prayed, the miracles He performed, and the life which He lived, was as the Man Christ Jesus, doing all this in the energy of the Holy Spirit. Our Lord exercised faith in the cursing of the fig tree. He presses home the lesson of the necessity of faith to the disciples. The word “God” is in the genitive case, showing here the object of faith.
Translation. And answering, Jesus says to them, Be constantly having faith in God.
Mark 11:23 – Swete has an illuminating note: “The Twelve were crossing the Mount of Olives; below them, between the mountains of Judaea and the mountains of Moab, lay the hollow of the Dead Sea. ‘Faith, cooperating with the Divine Will, could fill yonder basin with the mass of limestone beneath their feet.’ The metaphor was in use among the Rabbis….Faith is regarded as the normal attitude of the heart, not a sudden emotion or isolated act. Faith contemplates the effect as potentially accompanying its exercise, though the actual fulfillment may be delayed.” The word “doubt” is diakrino. The word means “to judge between two,” thus, a divided judgment, or a wavering doubt. The words “shall come to pass,” are present tense in the Greek text. More accurately, “comes to pass.” Robertson calls it a futuristic present. The words “whatsoever he saith” are rejected by Nestle.
Translation. Truly, I am saying to you, Whoever says to this mountain, Be lifted up and be thrown into the sea, and does not doubt in his heart but believes that which he says comes to pass, it shall be his.
Mark 11:24 – The word “faith,” therefore, indicates the logical connection between the contents of verse 23 and this verse. The idea is that since faith is the criterion of success in spiritual matters, therefore faith should be the constant attitude of the mind when one prays. The word “pray” is proseuchomai, “to offer a prayer addressed to God, to Him as the object of faith and the One who will answer one’s prayer.” The word “desire” is aiteo, used of prayer when one asks for something to be given. “Receive” is aorist, thus antecedent in time to the verb “believe.” Robertson says: “That is the test of faith, the kind that sees the fulfillment before it happens.” “Faith is the title deed of things hoped for ( Heb. 11:1 ).” Just as a title deed guarantees to the one whose name appears on it, the ownership of the property, even though he may not have it in his actual possession, so faith is the title deed that guarantees to the one exercising it, the answer to his prayer, even though that answer may be delayed, and the thing asked for not in his possession.
Translation. On this account I am saying to you, All things whatever when praying you also ask for, believe that you received, and they shall be yours.
Mark 11:25, 26 – The word “when” is hotan “whenever.” The standing posture when praying is not commanded here, nor is it the only posture allowed. The word merely calls attention to a practice among the Jews. The word “trespasses” is paraptoma, which means “a fall alongside,” thus “a fall from the right course,” thus, “a false step.” Nestle rejects verse 26, as do Westcott and Hort. The Revised Version puts it in a footnote.
Translation. And whenever you are standing, praying, forgive, if you have anything against a certain person, in order that your Father who is in heaven may forgive you your trespasses.