Genesis 2:2-3 - The Sabbath

And on the seventh day God ended his work which he had made; and he rested on the seventh day from all his work which he had made. And God blessed the seventh day, and sanctified it: because that in it he had rested from all his work which God created and made.

Let's not forget the Sabbath, for even God rested on the seventh day. All business should be conducted within the first six days of the week and no business should be conducted on the seventh day;

Genesis 2:13-14 - Six days thou shalt labour, and do all thy work: But the seventh day is the sabbath of the LORD thy God: in it thou shalt not do any work, thou, nor thy son, nor thy daughter, nor thy manservant, nor thy maidservant, nor thine ox, nor thine ass, nor any of thy cattle, nor thy stranger that is within thy gates; that thy manservant and thy maidservant may rest as well as thou.

Rest is not an option, it's a commandment;

Leviticus 23:3 - Six days shall work be done: but the seventh day is the sabbath of rest, an holy convocation; ye shall do no work therein: it is the sabbath of the Lord in all your dwellings.

Even Jesus needed time to rest;

Mark 6:31 - And he said unto them, Come ye yourselves apart into a desert place, and rest a while: for there were many coming and going, and they had no leisure so much as to eat.

The seven day period is sacred, as in the following examples:

• Genesis 7:4 - For yet seven days, and I will cause it to rain upon the earth forty days and forty nights; and every living substance that I have made will I destroy from off the face of the earth.
  
• Exodus 7:25 - And seven days were fulfilled, after that the Lord had smitten the river.
• Exodus 29:30 - And that son that is priest in his stead shall put them on seven days, when he cometh into the tabernacle of the congregation to minister in the holy place.
  
• 1 Samuel 11:3 - And the elders of Jabesh said unto him, Give us seven days' respite, that we may send messengers unto all the coasts of Israel: and then, if there be no man to save us, we will come out to thee.
  
• 1 Samuel 13:8 - And he tarried seven days, according to the set time that Samuel had appointed: but Samuel came not to Gilgal; and the people were scattered from him.
• Ezekiel 3:15 - Then I came to them of the captivity at Telabib, that dwelt by the river of Chebar, and I sat where they sat, and remained there astonished among them seven days
• Acts 20:6 - And we sailed away from Philippi after the days of unleavened bread, and came unto them to Troas in five days; where we abode seven days.
  
• Acts 21:4 - And finding disciples, we tarried there seven days: who said to Paul through the Spirit, that he should not go up to Jerusalem.
  
• Acts 28:14 - Where we found brethren, and were desired to tarry with them seven days: and so we went toward Rome.

Some more references to the Sabbath:

• Exodus 16:23 - And he said unto them, This is that which the Lord hath said, To morrow is the rest of the holy sabbath unto the Lord: bake that which ye will bake to day, and seethe that ye will seethe; and that which remaineth over lay up for you to be kept until the morning.
  
• Psalms 118:24 - This is the day the Lord hath made; we will rejoice and be glad in it.
• Matthew 12:1 - At that time Jesus went on the sabbath day through the corn; and his disciples were an hungred, and began to pluck the ears of corn, and to eat.
  
• Matthew 12:8 - For the Son of man is Lord even of the sabbath day.
  
• Mark 2:27 - And he said unto them, The sabbath was made for man, and not man for the sabbath:
  
• Hebrews 4:4 - For he spake in a certain place of the seventh day on this wise, And God did rest the seventh day from all his works.