undisturbed quiet: the calm of being safe and comfortable with nothing pressing in, a calm Scripture can either bless or condemn
This word names a condition rather than an action: nothing is pressing on you, nobody is threatening you, and there is enough. It stands close to the great Hebrew word for peace (שָׁלוֹם), and the two sit side by side in the prayer for Jerusalem, where peace is asked for the city's walls and this word for the palaces behind them. The difference is reach. Peace covers wholeness and welfare of every kind, while this word names only the undisturbed quiet of nothing going wrong. The describing word from the same root (שָׁלֵו) is used of the person or the countryside that is at ease; this noun names the ease itself.
The striking thing about it is that the same calm is a gift in one verse and a charge in the next. Proverbs prefers a dry crust eaten in quiet to a house full of feasting and quarreling, and the same book says the comfortable ease of fools is what destroys them. Ezekiel lists the sins of Sodom as pride, plenty of food, and untroubled ease while the poor around her went unhelped. Jeremiah has God speaking to a nation all through its untroubled years and hearing back, "I will not listen." A psalmist, using the same noun in a slightly different shape (שֶׁלֶו), admits that in his own comfortable ease he had told himself he would never be shaken.
Daniel puts the word to a third use, three times over, for a ruler who arrives while everyone is relaxed. Scholars read that phrase in two directions, either as the unsuspecting safety of the people who are attacked or as the friendly face the attacker puts on, which is why English versions swing between "when they feel secure," "without warning," and the older "peaceably." Either way, the calm is what lets the blow land.
Nuances
Whether the adverbial phrase bĕšalwāh in Daniel 8:25 and 11:21, 24 describes the unsuspecting security of those attacked (hence "unawares, without warning") or the feigned peaceableness of the aggressor himself (hence "peaceably, under cover of friendship").
- majorityThe phrase looks at the victims: they are living in security, so the assault comes upon them unexpectedly, and the idiom approaches the adverbial sense "unawares" or "without warning."; BDB, s.v. שַׁלְוָה; HALOT, s.v. שַׁלְוָה
- minorityThe phrase looks at the aggressor: he advances under a show of peace and friendly overture, in keeping with the deceit and flattery named alongside it in the same contexts.; J. J. Collins, Daniel (Hermeneia)