What was Big Willy Shakes going for?
Lancelot is a clown and a servant—first Shylock's and then Bassanio's. Like all Shakespearean clown figures, Lancelot's job is to fool around, make smart-alecky comments, and bag on all the other characters in the play. So we know we've got to take everything he tells us with a grain of salt. He is a kidder, after all.
But this is no joking matter. Shylock is a tricky guy to live with—for Lancelot and Shylock's own daughter, Jessica (who ditches him for a guy). When Lancelot leaves the "hell" house to serve Bassanio, we're reminded of how awful it is to live with Shylock because even a clown can't make a joke out of it.
In fact, Lancelot hates the house so much he plans to be out of there as fast as an eye twinkles… so pretty fast. We did a little digging and found that this phrase shows up in the Bible: "In a moment, in the twinkling of an eye, at the last trump: for the trumpet shall sound, and the dead shall be raised incorruptible, and we shall be changed" (1 Corinthians 15:52).
Not only that, but it's in a devotional from 1303 called Handlying synne: "yn twynkelying of an ye" (source). Hmm… is it just us, or is it no coincidence that both of these are religious works, and Shylock is known for his own religion (Judaism)? Maybe Shakespeare's having a little fun with religion here.
We know that Shylock tends to emphasize the differences between Jews and Christians. When Bassanio invites him to dinner, Shylock mutters "I will buy with you, sell with you, talk with you, walk with you, and so following, but I will not eat with you, drink with you, nor pray with you" (1.3.8). We should mention that some critics feel Shylock's disdain for Christians is totally justifiable because he's been trash-talked, spit upon, called a dog, and worse by a fair few of the Christian residents of Venice. Sure, we can see that.
It seems like there's not a scene that goes by in which some character isn't hurling anti-Semitic insults. So is it that much of a stretch to think he's hinting at religion here with this phrase? Perhaps Lancelot uses this saying knowing it's from Christian texts as one last nanny-nanny-boo-boo to Shylock (even though he's not there).