ˈjoÅbəˌlÄ“
7 is often considered the number of God or number of completion.
7 x 7 = 49
On the 49th year, God mandates in Leviticus 25:8-55 that the 50th year would be set apart for rest and redemption. The people, land and animals would rest and debts would be canceled.
It is a holy celebration.