饭前洗手是个好习惯。

Washing hands ante cibum is a good habit.

你应该总是在饭前洗手。

You should always wash your hands before meals.

玛丽饭前洗手。

Mary washes before meals.

在这种情况下，食物时时是众人一起分享的，于是饭前洗手很要紧，而且要遵守用右手吃东西的习俗（左手时时有其他用处）。

In these cases, food is often offered communally, which is why it's important to wash your hands before eating and observe the right-hand-is-for-eating and the left-hand-is-for-other-duties rule.