Lexicon :: Strong's G4003 - pentekaidekatos

The entire Israelite community departed from Elim and came to the Wilderness of Sin, which is between Elim and Sinai, on the fifteenth day of the second month after they had left the land of Egypt.

“The Festival of Unleavened Bread to the LORD is on the fifteenth day of the same month. For seven days you must eat unleavened bread.

“Tell the Israelites: The Festival of Shelters[fn] to the LORD begins on the fifteenth day of this seventh month and continues for seven days.

“You are to celebrate the LORD’s festival on the fifteenth day of the seventh month for seven days after you have gathered the produce of the land. There will be complete rest on the first day and complete rest on the eighth day.

“On the fifteenth day of this month there will be a festival; unleavened bread is to be eaten for seven days.

“You are to hold a sacred assembly on the fifteenth day of the seventh month; you do not do any daily work. You are to celebrate a seven-day festival for the LORD.

They traveled from Rameses in the first month, on the fifteenth day of the month. On the day after the Passover the Israelites went out defiantly[fn] in the sight of all the Egyptians.

Jeroboam made a festival in the eighth month on the fifteenth day of the month, like the festival in Judah. He offered sacrifices on the altar; he made this offering in Bethel to sacrifice to the calves he had made. He also stationed the priests in Bethel for the high places he had made.

In the fifteenth year of Judah’s King Amaziah son of Joash, Jeroboam son of Jehoash became king of Israel in Samaria, and he reigned forty-one years.

the fifteenth to Bilgah, the sixteenth to Immer,

They were gathered in Jerusalem in the third month of the fifteenth year of Asa’s reign.

But the Jews in Susa had assembled on the thirteenth and the fourteenth days of the month. They rested on the fifteenth day of the month, and it became a day of feasting and rejoicing.

He ordered them to celebrate the fourteenth and fifteenth days of the month of Adar every year

In the twelfth year,[fn] on the fifteenth day of the month, the word of the LORD came to me:

“At the festival that begins on the fifteenth day of the seventh month,[fn] he will provide the same things for seven days ​— ​the same sin offerings, burnt offerings, grain offerings, and oil.