In Donald Knuth's paper "Structured Programming With Go To Statements", he wrote: "Programmers waste enormous amounts of time thinking about, or worrying about, the speed of noncritical parts of their programs, and these attempts at efficiency actually have a strong negative impact when debugging and maintenance are considered. We should forget about small efficiencies, say about 97% of the time: premature optimization is the root of all evil. Yet we should not pass up our opportunities in that critical 3%."

Here's a link to the source paper, which confirms the quote:

https://www.cs.sjsu.edu/~mak/CS185C/KnuthStructuredProgrammi...