If you are living in Eretz Yisrael, holding on to a foreign passport is a way of stating that you really aren’t sure about staying in Israel, and need to have a place to flee if the country collapses or if the medinah survives but becomes fanatically anti-religious. There are some inconveniences in holding on to a foreign passport (and a lot of tax issues particularly for Americans), but the bottom line is that if the medinah is driven into the sea, the leading priority in all but one country in that region, you won’t be a stateless refugee.
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