Sentence:  Shylock: / ...Do as I bid you; shut doors after you: / <WSD>Fast</WSD> bind, <WSD>fast</WSD> find; / A proverb never stale in thrifty mind. 
Meaning of the word marked with <WSD> tags:  In a firm or secure manner, securely; in such a way as not to be moved; safe, sound (from 10th c.).