There are plenty of biblical allusions in the play, but one story in particular seems to stand out. That's the story of Jacob and Laban (from Genesis 25-35), part of which Shylock tells as a kind of family story. This passage is long but important:
When Jacob grazed his uncle Laban's sheep –
This Jacob from our holy Abram was,
As his wise mother wrought in his behalf,
The third possessor; ay, he was the third –
And what of him? did he take interest?
No, not take interest, not, as you would say,
Directly interest: mark what Jacob did.
When Laban and himself were compromised
That all the eanlings which were streak'd and pied
Should fall as Jacob's hire, the ewes, being rank,
In the end of autumn turned to the rams,
And, when the work of generation was
Between these woolly breeders in the act,
The skilful shepherd peel'd me certain wands,
And, in the doing of the deed of kind,
He stuck them up before the fulsome ewes,
Who then conceiving did in eaning time
Fall parti-colour'd lambs, and those were Jacob's.
This was a way to thrive, and he was blest:
And thrift is blessing, if men steal it not.
This was a venture, sir, that Jacob served for;
A thing not in his power to bring to pass,
But sway'd and fashion'd by the hand of heaven.
Was this inserted to make interest good?
Or is your gold and silver ewes and rams?
I cannot tell; I make it breed as fast:
But note me, signior.
Mark you this, Bassanio,
The devil can cite Scripture for his purpose.
An evil soul producing holy witness
Is like a villain with a smiling cheek,
A goodly apple rotten at the heart:
O, what a goodly outside falsehood hath! (1.3.13)
In Genesis, Jacob and his uncle Laban make a deal that Jacob (who takes care of his uncle's sheep so he can marry Laban's daughter Rachel) gets to keep all the striped and spotted animals. In this passage, Shylock relates the story of how, when Jacob placed striped branches in front of the sheep when they mated, the sheep gave birth to striped lambs. Jacob was pretty crafty and got super rich by doing this.
In this passage from the play, we can see two completely different interpretations of the same sacred text. Shylock sees Jacob's story as an example of human ingenuity. Antonio, on the other hand, sees Jacob's success as an example of God's providence. Antonio also accuses Shylock of using a biblical story to justify the practice of usury (lending money and charging interest) and refers to Shylock as a devil. Antonio is trying to undermine the fact that Jacob's story is just as important to Jews, like Shylock, as it is to Christians. So here we have a Christian and a Jew at odds over how a story from the Bible should be interpreted, which pretty much sums up how Christians and Jews are pitted against one another throughout the play.