It has had significance in almost every major religion. In the Old Testament the world was created in six days and God rested on the seventh, creating the basis of the seven-day-week we use to this day. In the New Testament the number seven symbolizes the unity of the four corners of the Earth with the Holy Trinity. The number seven is also featured in the Book of Revelation (seven churches, seven angels, seven seals, seven trumpets, and seven stars). The Koran speaks of seven heavens and Muslim pilgrims walk around the Kaaba in Mecca (Islam’s most sacred site) seven times. In Hinduism there are seven higher worlds and seven underworlds, and in Buddhism the newborn Buddha rises and takes seven steps. In Hindu weddings, the couple walks for seven steps Saptapadi, after which they are declared as husband and wife. They have to make seven rounds around the holy fire as a part of their wedding rituals.
7 continents in the world. 7 wonders of the ancient world. 7 colours in the rainbow. 7 musical notes. 7 phases of the moon. 7 days of the week. 7 brides for 7 sons.
Don't forget the Group of 7.
Seven has the highest probability of occurring as an addition when rolling dice.
A ladybug commonly has seven spots.
The number of rows in the periodic table of elements is seven.
Source: https://massart.edu/sites/default/files/Principles and Elements.pdf