Lorenzo says the following:

I must needs tell thee all. She hath directed
How I shall take her from her father's house,
What gold and jewels she is furnish'd with,
What page's suit she hath in readiness.
If e'er the Jew her father come to heaven,
It will be for his gentle daughter's sake:
And never dare misfortune cross her foot,
Unless she do it under this excuse,
That she is issue to a faithless Jew.
Come, go with me; peruse this as thou goest:
Fair Jessica shall be my torch-bearer.

Lorenzo, a Christian, says this with regard to Jessica, the daughter of Shylock the Jew. She and Lorenzo have fallen in love and plan to elope. In this passage, Lorenzo expresses a common Christian sentiment of the time. Jews were viewed with disdain and treated with contempt. They were seen as outsiders who had no right to be in Venice and were therefore not afforded the same rights and privileges extended to Christians. Jews were deemed money-grubbers because, as Antonio also states in the play, they lent money at interest. This was seen as a form of usury and was regarded as corrupt.

The xenophobia expressed here seems to have been a popular theme and also forms the basis of the plot in Shakespeare's play, Othello, where much the same kind of intolerance and racism finds expression through the characters of Iago, Roderigo and Brabantio in the same setting - Venice.

When Lorenzo says:

If e'er the Jew her father come to heaven,
It will be for his gentle daughter's sake:

... she is issue to a faithless Jew.

Jews were seen as heathen, almost savage, and were damned for their beliefs. The general idea was that they would not reach heaven because of this and their race were thus treated with utter contempt, so much so, that Antonio had, on occasion, even spat in Shylock's face and had publicly vilified and insulted him. Lorenzo is saying that the only reason why Shylock would ever forsake his own faith and become a Christian, would be for his daughter's regard.