'First Day' in the Bible

Seven days ye eat unleavened things; only -- in the first day ye cause leaven to cease out of your houses; for any one eating anything fermented from the first day till the seventh day, even that person hath been cut off from Israel.

And in the first day is a holy convocation, and in the seventh day ye have a holy convocation; any work is not done in them, only that which is eaten by any person -- it alone is done by you,

'On the first day of the month, in the first month, thou dost raise up the tabernacle of the tent of meeting,