And the dove came back to him in the evening: came back means returned to Noah and the boat from where it had left. It is not stated when the dove was released, whether in the morning or afternoon. Evening most probably refers to the late afternoon, when birds return to their nests for the night. To him is as in Gen 8.9.

And lo translates the Hebrew connective plus an interjection, which in prose usage calls attention to something of particular significance. See also 1.31, where it is rendered “behold.”

In her mouth: mouth here refers to the dove’s beak.

A freshly plucked olive leaf: freshly plucked translates a Hebrew term that is also used in Ezek 17.9 of “fresh-sprouting leaves.” The emphasis is on the fresh, green state of the olive leaf in contrast to a dried or dead condition. Some interpreters point out that an olive leaf would not be found at high elevations. Consequently a fresh olive leaf would have to be brought from lower altitudes and would mean that the water had subsided even in the valleys. However, it is unlikely that the narrator is calling attention to the olive leaf in contrast to some other family of tree leaves.

In areas where the olive tree is unknown, translators may speak of “a tree called olive,” in which “olive” is expressed through a loan word. If this solution is unsatisfactory, it may be possible to substitute a local tree, or to say simply “a fresh green leaf.”

So Noah knew that the waters had subsided from the earth: so introduces a consequence. Knew in this context means Noah “had learned, found out, realized.” Subsided translates the same word used in 8.8 and has the same sense as in 8.1. See there for comments. For from the earth see comments on verse 7.

Quoted with permission from Reyburn, William D. and Fry, Euan McG. A Handbook on Genesis. (UBS Helps for Translators). New York: UBS, 1997. For this and other handbooks for translators see here .