There are a few allusions on act 4. Specifically on scene 3, there’s a conversation between Malcolm and Macduff in which Malcolm wants to prove if Macduff is reliable and he says:
He (Macbeth) hath not touch'd you yet. I am young;
but something
You may deserve of him through me, and wisdom
To offer up a weak poor innocent lamb
T’appease an angry god.
(4.3.13-17)
This part makes an allusion to the offering of Christ, who is often seen as the “lamb,” therefore Macbeth should be seen as an “angry god.” This concept of offering an “innocent lamb” is also repeated in lines 50 to 56 of the same scene.
Malcolm also tries to convince Macduff that he and Macbeth are mischievous and bad:
MALCOLM
It is myself I mean: in whom I know
All the particulars of vice so grafted
when they shall be open'd, black Macbeth
Will seem as pure as snow, and the poor state
Esteem him as a lamb, being compared
With my confineless harms
MACDUFF
Not in the legions
Of horrid hell can come a devil more...
In evils to top Macbeth
(4.3.50-56)
Macbeth is compared to the devil himself for all the bad things he has done so far. But he will be conquered as Malcolm says it: “ripe for shaking”. This part can be compared in the Bible to the book of Nahum, in which says: “All thy strong cities shall be like fig trees with the first ripe figs: for if they be shaken, they fall into the mouth of the eater.” In this passage the “strong cities” refer to God’s enemies: the inhabitants of the city of Nineveh. These people are, like Macbeth, ready to be taken over. And Macbeth at the end gets all the bad things he received.
Also from act 4, scene 3: “…Angels are bright still, though the brightest fell, Though all things foul would wear the brow of grace, Yet grace must still look so.” Here they talk about angels and they specially refer to the brightest of them all (Lucifer) who fell from God’s grace. It also shows that sometimes everything is not what it seems.