They that sanctify … themselves in the gardens (comp. Isaiah 1:29; Isaiah 65:3; and see the comment on the latter passage). Behind one tree in the midst; literally, behind one in the midst. It seems quite impossible that "one" can mean "one tree," when no tree has been mentioned, and gardens do not necessarily contain trees.
The marginal rendering, "one after another," is also impossible. The "one in the midst" must have been either a hierophant who directed the ceremonies (Gesenius, Hitzig, Knobel, Delitzsch), or an image of a deity (Scaliger, Voss, Grotius, Lagarde, Cheyne).
In the latter case, we must suppose that the worshippers had a scruple about mentioning the deity's name, and were accustomed to call him "one," or "a certain one" (comp. Herod; 2.171). Isaiah adopts their usage.
Eating swine's flesh (comp. Isaiah 65:4). And the abomination. The word is used generically of all the "abominable things" forbidden to be eaten in Le Isaiah 11:4 -30, as the camel, the coney, the hare, the eagle, the vulture, the ferret, the chameleon, the lizard, etc.
The mouse. Probably the jerboa (see Le 11:20).