I've always found the insights of the prophet Isaiah alarmingly contemporary. One of the most striking is the outburst that we read in Isaiah 58. People don't always see it that way, of course. Frequently, the chapter is raided for reassurance. Doesn't verse 11 promise us, for example, that the Lord will guide us continually and satisfy our needs in parched places, and make us strong? Doesn't it assure us that we shall be like springs whose waters never fail? Well, yes, but only after some very straight talk about utter neglect of responsibilities and the dire need to mend our ways.
The context of Isaiah 58 is clear enough. The people of God are very sure that they are doing all the right things before God. They are caught up in prayer and worship, they call on God to give judgments (probably on the "unrighteous"), and they profess their delight in knowing God's ways. They even go through rituals of self-denial so that their religious zeal cannot be in any doubt. But then it dawns on them with some surprise that God doesn't seem to be giving the right response. They ask, "Why do we fast, but you don't see? Why humble ourselves but you don't notice?" (58:3). God's response through Isaiah must have come as a bit of a shock, as it would to many of us Christians today: "Is that what you call a fast—serving your own interests, quarrelling, and oppressing all your workers?" (58:3-4, paraphrase).