Number 7 in Judaism
Menorah -
The Seven-branched Candelabrum
The Menorah has been a symbol for Judaism for about 3000 years.
Exodus 25:31-40 explains to the last detail how the Menorah is to be made.
"And you shall make a lamp stand of pure gold.....and there shall be six branches going out of its sides, three branches of the lamp stand out of one side of it and three branches of the lamp stand out of the other side of it;........"
It was used in the ancient Holy Temple in Jerusalem.
The Seven-branched Menorah is a reminder of the words written in Isaiah 42:6, "....to be a light to all nations,..."
It is also said that the Menorah is a symbol of the burning bush seen by Moses. Many say it also is a symbol of the seven days of creation. 
It is now the emblem of Israel.
The Seven Days of Sukkot
The sukkot is known as the "Festival of the Booths".
This holiday is a reminder of the days wondering through the desert after the escape from the slavery in Egypt.
"You shall live in booths seven days in order that future generations may know that I made the Israelite people live in booths when I brought them out of the land of Egypt:
I am the Lord your God." Leviticus 23:42-43
Sukkot is a harvest festival and also a joyous festival. For this holiday, the Jews will build a Sukkah, a kind of temporary hut. Jews will eat their meals in the Sukkah when possible.
Jews may follow a custom of inviting seven symbolic biblical Ushpizin (guests) to their Sukkah. The seven symbolic Ushpizin are: Abraham, Isaac, Jacob, Joseph, Moses, Aaron, and David.
Some Jews also extend the invitation to seven female biblical figures: Sarah, Rebecca, Leah, Rachel, Miriam, Abigail, and Ester.
It is also customary to invite guests to dine in the Sukkah and visit the Sukkah of friends. The special Four Species are also an important part of the Sukkot festival.
On the seventh day of the Sukkot, there is a procession that will make seven circuits around the Bimah (platform where the Torah is read). The seventh day of Sukkot is called "Hosanah Rabbah" (the Great Hoshanah).
The Simchat Torah – The Rejoicing of the Torah – The Seven Hakafot
Immediately after the Sukkot is the festival of the Simchat Torah.
Simchat Torah is the day when the last part of Deuteronomy is read, followed by the first chapter of Genesis. This signifies the cycle of the Torah. It has neither beginning nor end.
The Torah rolls are paraded around the sanctuary in the synagogue seven times.
This is called the hakafot. 
This festival includes lots of dancing and singing.
Often the congregation will continue dancing with the Torah out on the streets making it an extremely joyous festival.
This is a genuine happy celebration. The children enjoy plenty of candy. Many will enjoy lots of good wine.
The Simchat Torah is absolutely party time!
Seven and the Jewish Wedding
Many Jews refer to a wedding as a simchah, which means a joyous event.
A Jewish wedding may take place anywhere. It is required that the couple stands under a chuppah, a wedding canopy. It is a symbol of their new home.
The groom is led to the chuppah by two men, often his father and father-in-law. Likewise the bride is led to the chuppah by two women, most often by her mother and mother-in-law.
The bride is led seven times around the groom. This may symbolize the seven days of creation and that the couple will also create new life.
The bride and groom drink from the wine and the groom places the ring on the bride’s finger as he says: "You are hereby sanctified to me with this ring according to the Laws of Moses and Israel."
In the second part of the ceremony the Seven Blessings are recited. The ceremony concludes with the breaking of the glass, as a reminder of the destruction of the temple. Finally the entire congregation shouts "Maz'l tov", meaning "Congratulations" or "May you enjoy a good fortune".
Shavuot – Seven Weeks
Shavuot is celebrated to commemorate Moses receiving the Torah, with the list of the Ten Commandments, on Mount Sinai. This happened seven weeks after they had departed from Egypt.
Many may choose to stay awake all night studying the Torah starting Shavuot Eve.
During Shavuot many will eat cheese cake and other dairy foods as the Jews in the desert were not yet sure about all the laws concerning the preparation of meat products.
Shavuot is also a Harvest festival. At the time of the Temple, Jews would bring offerings of the first harvest to the Temple in Jerusalem. Farmers would bring the Seven Species written about in Deuteronomy 8:8; wheat, barley, grapes, figs, pomegranates, olives and dates. These are the Seven Species the land of Israel is blessed with. The Israelites would also offer two loaves of bread from the wheat harvest.
During Shavuot the Book of Ruth is read at the morning service.
The synagogue may traditionally be decorated with plenty of flowers. Shavuot is a joyous festival.
“Ruth in Boaz’s Field” 1828 Julius Schnorr von Carolsfeld. National Gallery, London
Sitting Shivah
Shivah is a period of mourning. Shivah means "seven", this refers to the first seven days of mourning. Mourners who sit Shivah are the seven closest relatives of the deceased: father, mother, son, daughter, brother, sister and spouse.
Before or at the funeral ceremony the mourners perform "Keriah", They rend (tear) a garment as a symbol of separation. It should be a garment worn over the heart, for example a shirt or blouse. This has roots in Genesis 37:34, when Jacob was misled to believe his son Josef had been killed by wild animals he rent his garments. Many Jews may wear a torn, black ribbon pin. The torn garment or the torn black ribbon is worn throughout the Shivah.
The mourners sit Shivah in the home of the deceased or the home of the mourners. They go directly to the home after the funeral. A large candle burns during the Shivah. During the Shiva friends and neighbors bring food so that the mourners do not have to prepare meals for themselves.
The first meal is called "The meal of recovery". The mourners do not leave the house during Shivah, except for Sabbath. Public mourning is forbidden on Sabbath, but it still counts as one of the seven days.
There are some rules and restrictions during Shivah. Some of them are:
The mourner should sit on a low stool or on the floor.
All mirrors should be covered during Shivah.
The mourner must not wear leather shoes.
The mourner must not wash or iron clothes, nor wear new clothes.
The mourner must not shave, cut their hair, nor cut their nails.
The mourner must not cook nor prepare food using heat.
The mourner must not study the Torah, except for the Book of Lamentations and the book of Job.
The mourner must abstain from sex.
The mourner should not do business except for emergencies.
The Shivah ends on the afternoon of the seventh day after the funeral. The mourners leave the Shivah house for a walk together with friends and family. After the Shivah, the next period of mourning begins. It is called the shloshim and lasts for thirty days after the burial.
The Seven Laws of Noah
The Seven Laws of Noah are also called the Noahide Laws. According to the Talmud, these laws were given to Noah by God as binding laws for all mankind. As every person on earth is a child of Noah, these laws apply to all of mankind, not only the Jews.
It is said that any non-Jew who follows these laws is assured a place in the world to come.
Six of these laws were given first to Adam in the Garden of Eden. The seventh law "eating flesh from a living animal" was added after the Flood of Noah.
There is a growing movement of non-Jews who have accepted these Laws of Noah and have chosen to live their lives according to them.
The movement is called the B'nei Noach, Children of Noah.
The rainbow is the modern symbol of the Noahide Movement. This is in remembrance of the rainbow that appeared after the Great Flood of the Bible.
1. You shall have no other idols before God
2. You shall not blaspheme God's name
3. You shall not murder.
4. You shall not steal.
5. You shall not commit incest and adultery, nor male homosexual intercourse.
6. You shall establish courts of justice.
7. You shall not eat the flesh cut from a living animal.
(This also implies: Do not eat or drink blood)