'First Day' in the Bible

And, on the first day of the unleavened bread, when they were slaying the passover, His disciples say to Him, "Where dost Thou wish that we, going, prepare, that Thou mayest eat the passover?"

And, very early on the first day of the sabbaths, they come to the tomb, the sun having risen.

And, having risen early on the first day of a sabbath, He appeared first to Mary Magdalene from whom He had cast out seven demons.