proper and morally good behavior
—When you move away from your parents, you need to choose the right friends so that you’ll stay on the straight and narrow.

According to Jesus, while following God is the best path, it isn’t the easiest. He said,

Enter through the narrow gate, because the gate is wide and the way is spacious that leads to destruction, and there are many who enter through it. But the gate is narrow and the way is difficult [strait is the gate, and narrow is the way] that leads to life, and there are few who find it. (Matthew 7:13,14)

The strait of the King James Bible is not often used in modern English, which is why it’s now spelled as straight. The words straight and strait not only have different spellings, but they have different definitions, as well. Straight means “not crooked,” while strait means “narrow, confined, or strict.” Strait has not gone away completely, as it still appears in phrases such as strait jacket (“a piece of clothing used to bind a person’s arms tightly to his sides”), and strait-laced (“following a very strict morality or etiquette”).