To keep ourselves unspotted from the world we are to go unto the house of prayer to offer up our sacraments. (v.9) We offer a broken heart and contrite spirit, then take the bread and water to repent and show our commitment to keep God's commands.
The Sabbath was appointed unto us to rest from our labors, and pay our devotions to the most High. We are to offer our oblations (footnote sayd time, talents or means) unto God. (v.12)
I've often thought it somewhat ironic that Sunday is supposed to be a day of rest, when it is often the busiest day for me. I've never been bitter or sarcastic about it, but made of joke of it like I know many do.
But after reading v. 12, I don't think I'll joke about it anymore. God knew there is much to be done to build His kingdom, and much of that work would be done on Sundays. While they are a day of rest from our worldly cares and labors, they are not a day of rest from the things of God. We are supposed to offer our time and talents to God on that day.
There were some things about fasting that I found interesting -- I've never caught them before. Vs. 13-14 say: And on this day thou shalt do none other thing, only let they food be prepared with singleness of heart that thy fasting may be perfect, or, in other words, that thy joy may be full. Verily, this is fasting and prayer, or in other words, rejoicing and prayer.
God is telling us that fasting should be rejoicing. We are to prepare our food in simplicity, so that we aren't spending 2 hours in the kitchen while we're fasting. If we follow this, then fasting will be more of a joy, which it should be. I'll be the first to admit that spending any time in the kitchen on fast Sunday takes the joy out of fasting. God isn't giving us a commandment to prepare the easiest meals on Sunday, but trying to help us. If we want our fast to be perfect, and not resent the fact that we aren't eating, just don't spend a lot of time in the kitchen!!
Another verse I like is 21. "And in nothing doth man offend God, or against none is his wrath kindled, save those who confess not his hand in all things, and obey not his commands."
Showing our gratitude is pretty important.