'First Day' in the Bible

In the first day you shall have a holy convocation: you shall do no regular work on it.

Speak unto the children of Israel, saying, In the seventh month, in the first day of the month, shall you have a sabbath, a memorial of blowing of trumpets, a holy convocation.

On the first day shall be a holy convocation: you shall do no regular work on it.

Also in the fifteenth day of the seventh month, when you have gathered in the fruit of the land, you shall keep a feast unto the LORD seven days: on the first day shall be a sabbath, and on the eighth day shall be a sabbath.

And you shall take on the first day the fruit of choice trees, branches of palm trees, and the boughs of leafy trees, and willows of the brook; and you shall rejoice before the LORD your God seven days.