JESUS= /dʒi:zəs/ 
The English name "Jesus" comes from Latin "Iesus", which comes from Greek "Iesous", which is the transliteration of the Aramic word "Yesuah", which comes from the Hebrew name "Yehosua" ("Joshuah" in modern English, "Josué" in modern Spanish, etc) which means "Yahweh rescues", that is, "God saves".

REPENTANCE= The act of repenting. To repent is to regret the wrong you have done plus a will to change your wicked ways and be good again. When John the Baptised preached about repentance, he was talking about the need for a complete change in your life, so baptising was a symbol for cleaning all your past wrongs and starting again a new life with a new purpose.

BELOVED= /bɪlʌvɪd/ Dear, precious, loved.

WHOM= After preposition we don't use the form "who" but "whom".

BEHOLD= (old fashioned) Look!
In modern English we still say "Beauty is in the eye of the beholder" (beholder = a person who beholds, who looks). This proverb means that beauty is not an inherent quality somebody has, but an aesthetic judgement somebody else makes on your appearance, so even people generally considered ugly may look beautiful to some other people.

THE LAMB OF GOD= Jesus.
This theological concept of Jesus as "the lamb of God" is very important to understand what happened with Jesus. For centuries, the Jews had been waiting for the coming of a Messiah, a leader sent by God who would liberate them and who would start a kingdom of love and justice for them. In Jesus' times, with Judea harshly oppressed by the Roman Empire, most people believed or hoped the Messiah would be a king or a warrior who would fight the Romans away and liberate them politically. Some others, not many, thought that the Messiah's liberation might be of a different kind, a deeper liberation, liberation from the bondage of sin and death. And probably only a few of them, if any, thought of the Messiah as "the servant of God", as Isaiah had described it about 500 years before: 
"He was oppressed and treated harshly, yet he never said a word.  He was led as a lamb to the slaughter.  And as a sheep is silent before the shearers, he did not open his mouth.  From prison and trial they led him away to his death.  But who among the people realized that he was dying for their sins - that he was suffering their punishment?  He had done no wrong, and he never deceived anyone.  But he was buried like a criminal; he was put in a rich man's grave." (Isaiah 53, fragment)
So when John the Baptists said "Behold, the lamb of God", he suddenly was recognising in Jesus the Messiah, and more than that, a Messiah who came as the "lamb" prophesized about by Isaiah; not the expected warrior, but the humble and peaceful servant of God.

THE SPIRIT= The Holy Spirit (also called "The Holy Ghost"), that is, God.
In the Trinitarian Christian view of the nature of God, God is considered to be one only being but possessing three different manifestations: 1- The Father, 2- Jesus (the Son) and 3- The Holy Spirit. All three manifestations are the same one and only God, but they can interact with each other and with others. Jesus became flesh and lived here on earth as a full man, so he could show us the way. While he was a man, he had to go through the usual problems and limitations any other man had to face, finding his way to God, being God as he was himself. ("Therefore he had to be made like his brothers in every respect" Hebrews 2:17)

GIVE UP= If you give up something, you decide to stop having it or using it or doing it.
- You smoke a lot. You should give up smoking before it's too late.
- I'm on a diet so I had to give up sweets and cakes.

SHIELD= A shield was a piece of armour held in your had to cover you and protect you from the sword of the enemy (see picture). Metaphorically, your shield is your protection, whatever keeps you safe from outside dangers.

ABIDES= (old fashion or literary) Lives, inhabits.

ARE YOU WILLING...?= Do you want...?
The word "willing" comes from the verb "will", a verb that often conveys the idea of volition, so it's similar to "want":
- Will you come to my party? (invitation) = Do you want to come to my party?
- I don't know, and she won't tell me = She refuses (doesn't want) to tell me
You will find more examples of this "will" expressing volition in this text, together with the "will" expressing future:
- Wait here and you will see = if you wait here, you're going to see what I mean.

CAN WE= When we begin a sentence with the word "only" or "not only", we usually invert the order of Subject+Verb:
- Only today did I see her = I saw her today for the first time, I didn't see her until today.
- Not only can you sing well, but you also can dance beautifully!

COMMAND= (formal) Order.

LOAVES= plural of "loaf". A loaf of bread is a unit of bread, the complete object. If you break a loaf into pieces, you have pieces of bread. (see picture)

UPON= (old fashioned or literary) On. If you "call on" something, you summon it, you order or request it to perform something.

CRUSH= Destroy or stress by pressure (for example you can crush an orange to make orange juice).

STARVING= If someone is starving, they are dying because they have no food. We also use it metaphorically to say that we are very very hungry.

YOU'RE MISSING THE POINT= You don't understand the real message of this conversation/situation.

MANKIND= Humanity, all men and women, the human species.

WILLS= Wants.
As we said above, you often use "will" to express volition (= want). But in the past the verb WILL was the Saxon word for volition, and then the verb WANT came with the Viking invasions to mean the same, so WILL began to be used to express future and other ideas, though very often retaining the original volition meaning. Nevertheless, that ancient WILL which was not an auxiliary but a normal verb meaning "want", still survives, though it sounds very formal or old-fashioned:
- Do as you will = Do whatever you want.
- He wills to help you (old fashioned)= He's willing to help you = He wants to help you.
- Will you help me? = Do you want to help me?
- If you will come, I will tell you = the first WILL means "want", and the second expresses future: if you want to come, I'm going to tell you.

PEASANT= /pezənt/ A poor country person; a low-class labourer, especially those who work in the fields.

MY FATHER'S WILL= God's desire, what God wants. 
Here "will" is a noun, and it means something similar to: desire, determination, wish.
- Your will is my command = I'll do anything you want (anything you want to do, your will, is like an order I receive to do it and please you).
- This is an old copy of Shakespeare's last will = your last will is a legal document where you write down instructions to be carried out after you die, especially how your possessions should be shared among your family and friends.

FOR YOUR OWN PURPOSES= To get a personal benefit.

THE STAKES= The way the situation works, "the game", how things are.

SECOND IN COMMAND= If you are second in command, you are the second most powerful person, but there is still a person more powerful above you, so you can give orders to all the rest, but that person above you can give orders to you.

BOW DOWN= To lower your head (or body) as a sign of respect, reverence or worship.

REWARD= A compensation or gratification you get for doing something.

AWAY WITH YOU= Go away from me.

SATAN= One of the names of the Devil, its most common name. Satan is the spirit of evil, he represents evil as opposed to good. Some consider Satan a real being, an evil spirit who can't confront God, but who is free to act in this material world to test people and try them. Others consider him a metaphor for the evil part of us, that "wicked voice" inside our head who pushes us to do wrong.

FOR= Because.

BY + -ING= We use the preposition BY followed by -ING when we want to express how to do something. Compare:
- He opened the door listening to music = He was listening to music when he opened the door.
- He opened the door by pressing a button = He pressed a button to open the door (how did he open the door? - by pressing a button)