And when is literally “and it will happen that,” so the idea of “if” (New American Bible) should be avoided. In time to come is the word for “tomorrow,” but here it means “In the future” (Good News Translation, Contemporary English Version). Your son asks you probably includes the daughter as well, so New Revised Standard Version has “When … your child asks you.” “Your children” (Contemporary English Version) is also possible. The you is singular. What does this mean? refers to “this observance.” One may also say “Why are you doing this?” You shall say to him introduces the exact words to be spoken by the father to the child.

By strength of hand refers to Yahweh’s power, as in verse 9.

The LORD brought us out of Egypt includes the parents but may exclude the children (see verse 8). The Hebrew language, however, did not distinguish between inclusive and exclusive plural. Therefore, in cultures where the exclusive form of us is used only when the addressee is intentionally excluded, the inclusive form should be used. These words were to be spoken for generations to come, so that through this ritual all Israelites will be able to feel themselves included in the deliverance from Egypt and come to understand Yahweh’s deliverance anew. (See also the discussion at 12.27.)

From the house of bondage is the same as verse 3. See the discussion there.

Quoted with permission from Osborn, Noel D. and Hatton, Howard A. A Handbook on Exodus. (UBS Helps for Translators). New York: UBS, 1999. For this and other handbooks for translators see here .