Deuteronomy 16:5-9

5You must not sacrifice the Passover in any town the Lord your God gives you 6except in the place he will choose as a dwelling for his Name. There you must sacrifice the Passover in the evening, when the sun goes down, on the anniversary of your departure from Egypt. 7Roast it and eat it at the place the Lord your God will choose. Then in the morning return to your tents. 8For six days eat unleavened bread and on the seventh day hold an assembly to the Lord your God and do no work. 9Count off seven weeks from the time you begin to put the sickle to the standing grain.