On God’s instruction, the children of Israel ‘borrow’ valuable items from the Egyptians, thus leaving Egypt with great wealth. This presents an obvious moral difficulty because they never return what they borrowed.
- Ibn Ezra affirms that the children of Israel did indeed trick the Egyptians, but that this was entirely licit because all property belongs to G-d and he may transfer it from one person to another when He wishes. In addition, the Egyptians only lent their goods to the Hebrews because God had given them grace in the eyes of the Egyptians. Finally, the deception was an essential component of tempting Pharaoh to pursue the Hebrews thus enabling the great kiddush HASHEM at the Sea of Reeds.
- Rashbam shows that the verb ‘to borrow’ [ש א ל] can be used to refer to a permanent transfer of property and claims that is the case here. On these lines, Rabbeinu Bahya argues that this gift was an act of justice both because of the many years the Hebrews had been unjustly put to work and because a slave should always be sent away with sufficient property to start a new life.
- Bechor Shor suggests that when the Hebrews asked the Egyptians for their possessions, they really thought they were borrowing them for the festival in the wilderness to return them later.
- Rashi writes that the deception was necessary in order to fulfil the prophecy given to Moshe at the covenant between the parts that his descendants would leave Egypt with רכוש גדול.
For more on parshat Va’eira, see Haggadah Berurah, the Haggadah that helps you tell the story of yetziat mitzrayim.
With all due respect, none of these explanations seem plausible to me. Borrow means borrow, meaning eventually returning to the original owners, in this case the Egyptians