This  - "This" is translated from a Greek adjective that means "this," "that," "the nearer." Without a noun, it has the sense of "this one" or "that one."

is -- The verb "is" here is the common form of "to be" in Greek. It means to have a certain characteristic or remain in a certain condition. It also equates terms or assigns characteristics.  The word also means "to exist" and where it doesn't connect to characteristics or conditions.

he, -- This is from the third-person, singular form of the verb.

of - (CW) The Greek word translated as "of" means "around" when referring to a place, but in referring to a subject, it means "about," "concerning," "on account of," and "in regard to." This is the way Jesus usually uses it. It is not the word form usually translated as "of."

whom -- The word translated as "whon" is a demonstrative pronoun ("this" "that"), but it often acts as a pronoun, "he," "she," "it," "which," "what," "who," "whosoever," "where," "for which reason," and many similar meanings.

it -- This is from the third-person, singular form of the verb.

is -- This helping verb "is" indicates that the verb is passive. Helping or auxiliary verbs are needed to translate the Greek verb forms into English.

written, -- (WT) "Written" is the Greek verb that  means "to mark," "to express by written characters," "to write a letter," "to write down [a law]," and so on. The form is passive participle of an action completed in the past, "having been written."

Behold, -- "Behold" is a verbal command meaning "See!" and "Look!" It is from the most common word meaning "to see" in Greek. In a humorous vein, it is also an adverbial exclamation like we use the phrase "ta-da" in a magic show, or "voila" in French which means "see there". "Look here!" or "See there!" comes closest in English. Jesus uses it both ways.

I -- This is from the first-person, singular form of the verb.

send --- (CW) The "send " here is a word that means "to send off" and "dispatch." It is the source of our word "apostle." This word is not the simple "send" but a more complex one that means "send out" or "send from." CW --Confusing Word -- The "sent" does not capture the word's specific meaning of "sent off" or "sent out."

my -- "My" is the first-person possessive singular pronoun, "my," "me," and "mine." Usually follows the noun so, "of mine." 

missing "the/this"  -- (MW) The untranslated word is the Greek definite article," the," which usually precedes a noun and, without a noun, takes the meaning of "the one." Before an adjective or a particle, it changes the following word to act like a noun. The Greek article is much closer to our demonstrative pronouns ("this," "that," "these," and "those"). See this article for more. 

messenger -- "Messenger" is a noun meaning "messenger" and "envoys" though it became to mean "semi-divine beings" in later use from its use in the NT, which is usually translated as "angels." Jesus uses this word to describe the means by which Jesus communicates to us and our thoughts.

before --  (CW) The Greek word translated as "before" means (of place) "before," "in front of," (of time) "before," (of preference), "rather than," "more than," and so on. This is not the same Greek word translated as "before" earlier in the verse.

thy  -- The word translated as "your" is the genitive form of the singular, second-person pronoun, which is most commonly the possessive form.   As a genitive object of a preposition, as here, it means a movement away from something or a position away from something else.

face, -- The Greek word translated as "faces" means "face" , "façade", "one's look", "dramatic part", "character", and other other similar ideas.

which -- The word translated as "which" is a demonstrative pronoun ("this" "that"), but it often acts as a pronoun, "he," "she," "it," "which," "what," "who," "whosoever," "where," "for which reason," and many similar meanings.

shall -- This helping verb "shall" indicates that the verb is the future tense. Helping or auxiliary verbs are needed to translate the Greek verb forms into English.

prepare - "Shall prepare" is a word that means "to equip," "to prove," "to construct," and "to prepare oneself." It is in the future tense. Christ uses this word only in this quote here and in Luke 7:26, the parallel quote in Luke. A

completely different Greek word is used in the Septuagint. A word that I cannot find a good Greek definition of. 

thy -- The word translated as "your" is the genitive form of the singular, second-person pronoun, which is most commonly the possessive form.  This pronoun follows the noun so "of yours."

missing "the/this"  -- (MW) The untranslated word is the Greek definite article," the," which usually precedes a noun and, without a noun, takes the meaning of "the one." Before an adjective or a particle, it changes the following word to act like a noun. The Greek article is much closer to our demonstrative pronouns ("this," "that," "these," and "those"). See this article for more. 

way  -- "Way" is from a word meaning "the way" or "the road" but which is used symbolically to mean "a way of doing things" or "a philosophy of life." In Acts, followers of Jesus are described as those "belonging to the way."

before  -- The Greek word translated as "before" means "in front of" referring to place and when used to apply to time means "beforehand."

thee -- The word translated as "thee" is the genitive form of the singular, second-person pronoun, which is most commonly the possessive form.  As a genitive object of a preposition, as here, it means a movement away from something or a position away from something else.