SHAVUOT IS TO BE CELEBRATED BY BOTH JEW AND NON-JEW

Deuteronomy 16:10 And you shall keep the feast of weeks unto the LORD thy God with a tribute of a freewill offering of thine hand, which you shall give unto the LORD thy God, according as the LORD your God has blessed you:

Deuteronomy 16:11 And you shall rejoice before the LORD your God, you, and your son, and your daughter, and your manservant, and your maidservant, and the Levite that is within your gates, and the stranger, and the fatherless, and the widow, that are among you, in the place which the LORD your God hath chosen to place his name there.