In the Bible, there is a day called Sabbath day. Sabbath day is the 7th day of the week which in our understanding is generally known as Sunday.
Sunday is a day set aside for every Christian all over the world to go to church and worship God. In Nigeria, it is a special day for the Christians where in some cases, some will postpone all the commercial activities and either rest or attend church service.
In the book of Genesis 2:2, on the seventh day God had finished his work of creation, so he rested from all his work.
The context of the book of Genesis 2:2 is so symbolic for all Christians where God himself had already shown the way. Every Christian honor Sunday as the only day of the week where God Himself set aside for rest and to worship him.
Therefore, Sunday is important for all Christians in the world, because it is a special day ordained by God himself for mankind to rest as well as worship him.