Charles Ellicott Commentary Hosea 2:15

"And I will give her her vineyards from thence, and the valley of Achor for a door of hope; and she shall make answer there, as in the days of her youth, and as in the day when she came up out of the land of Egypt." — Hosea 2:15 (ASV)

From there — i.e., away from there, meaning, as soon as she has left the wilderness of exile and discipline. The valley of Achor (or trouble) was associated with the disgrace and punishment which befell Israel on her first entrance into Palestine (Joshua 7:25–26), but it would in later days be regarded as the threshold of a blessed life. The sorrowful associations of the past were to be illuminated with happy anticipation.

Sing may suggest a reference to the dances and responsive songs at the village festivals, as well as to the triumphant strains of Exodus 15:0.