'Acceptable' in the Bible

Thus says Yahweh, "In an acceptable time have I answered you, and in a day of salvation have I helped you; and I will preserve you, and give you for a covenant of the people, to raise up the land, to make them inherit the desolate heritage:

Is such the fast that I have chosen? the day for a man to afflict his soul? Is it to bow down his head as a rush, and to spread sackcloth and ashes under him? Will you call this a fast, and an acceptable day to Yahweh?