This short verse seems inscrutable, but only because it is one of the most poorly translated. Commentaries refer to it as "obscure" and "not clear," but only because they either can't imagine  the situation or study the Greek, nor can they imagine hasThis statement is likely the response to a question, which was not recorded. Accurately translated, it was likely a lighthearted response to a serious question about his wounds. There are also several plays on words here that are lost in translation.  However, several words here may have been euphemisms where the complete meaning is lost. The meaning revolves around three words, one of them unique, on of them used in only one other  verse, and one that is only used in another context, opposite from how it is translated.

The word translated as "for" introduces a statement of fact or cause. Jesus seems to use it most commonly as an answer to a question. We can tell this because it usually is followed by a change of context, as we see here. This has nothing to do with the previous verse of asking the mountains to fall.

The "if" here expresses a condition but it means nothing regarding whether that condition is met or not. It also means "if ever" and "whenever."  There are two "if" words in Greek and the type of "if/then" statement it is depends on this word and the form of the verb.

The Greek word translated as "they do" has the primary meaning of "making" or producing" something or "causing" or "performing" as service. It describes a productive action.  It is not as broad a word as the English "do", which covers all actions, productive or not. The form is one of possibility, which makes this the most common form of "if" statement. This verb comes at the end of the clause in Greek, which is standard for an "if" clause.

The "these things" is a pronoun that can mean "this" or "that," the nearer or the further depending on usage. As an adverb it can mean "therefore" and "that is why." It is not typically used as an adjective. The form, plural neutral, adds the "things".  From the context, this most likely refers to the marks made by a staff that someone used to beat him..

The word translated as "in" also means "within", "with," "by:, or "among"  and more. It takes two forms of object, the one following this "in" has the broadest range of meaning. However, the next occurrence of this word is followed by another form of the word that is less common and has fewer meanings. Here, the most likely meaning is "with" in the sense of "by".

"Green" is  from a Greek adjective  that means "wet," "moist," "fluid," "soft"., "pliant", "subtle," "smoothly flowing", "moist with wine," "melting," etc. In English, we would say "fluid". It doesn't refer to the color. The meaning of "flexible" refers to the next word, while the meaning "wet" is the basis of the word play.

The Greek word translated as "tree" means "wood,"  "firewood", a "piece of wood", "cudgel", and various wooden instruments of punishment. It also means the "wood" of a tree or of a table. When referring to a person, it means "blockhead".  In all its other uses by Jesus, this word is translated as "staves", referring to the clubs those arresting him carry. However, here it seems to refer to the marks made by the beating or whipping he is given. The implements with which he was beaten had wooded handles. However, as a play on words, it could also refer to the blockhead that beat him.

The word translated as "what" means primarily "anything" or "anyone," but Jesus often uses it to start a question so it means "who", "what", or even "why". Here it is clearly a question, "what".

From the translation of "shall be done" you would think that this was the same word translated as "do" earlier in the verse. You might also think it was in the future tense. Neither is true. The word translated as "shall be done" means "to become," that is, to enter into a new state. In Greek, especially as used by Jesus, it is the opposite of "being," which is existence in the current state. When referring to events, it means "happen". The form is not the future tense, but the form of possibility, "might happen".

The word translated as "in" also means "within", "with," "by:, or "among"  and more. Earlied in the sentence it was used with one form of object, but here it is used with another word form. This clearly indicates that its meaning is different.  Here, the most likely meaning is "with" in the sense of "by" but with this word form the meaning is limited to   "into", "on", and "for."  Here, the meaning is obviously "on".

"The dry" is from an adjective that Jesus only uses in one other place to mean "dry land" but the word itself means "dry."  Here, it is a play on the earlier "fluid". Since it has no noun, the sense is "the dry one", referring to a wooden torture implement. It this case, that is obviously the "cross" or, more accurately, the stake, on which Jesus was hung.