The word plunder
is also translated in other versions as steal,
plunder,
or borrow
(but borrowing something without returning it is the same as stealing). It is not stealing. The Israelites ask their Egyptian neighbours for it (Exodus 11:2 and Exodus 12:35). To plunder is a way of expression. In this order we see:
God’s promise
This is the fulfillment of God’s promise to Abraham. Genesis 15:14: But I will bring judgment on the nation that they serve, and afterward they shall come out with great possessions.
God’s power
Usually defeated nations are plundered by warriors, but Egypt will be plundered by women and children!
God’s justice
Hundreds of years the Israelites have been slaves, now they get a reward. In Deuteronomy 15:13 God gives the law to not send slaves away empty-handed. His motivation is: Remember that you were a slave in the land of Egypt, and the Lord your God redeemed you
(Deuteronomy 15:15).
God’s glory
The silver and gold are used to build the tabernacle, God’s dwelling place among the people after the covenant of Sinai (see Exodus 35:1–35). (After the Babylonian exile the Persian king Cyrus also gave silver and gold for the rebuilding of the temple in Jerusalem, Ezra 1:2–4).
21 And I will give this people favor in the sight of the Egyptians; and when you go, you shall not go empty,