Saturday is the sabbath day, from Friday sunset to Saturday sunset.
The bible passages below prove that the people rested the day after Jesus died:
Luke 23:52-56 King James Version (KJV)
52 This man went unto Pilate, and begged the body of Jesus.
53 And he took it down, and wrapped it in linen, and laid it in a sepulchre that was hewn in stone, wherein never man before was laid.
54 And that day was the preparation, and the sabbath drew on.
55 And the women also, which came with him from Galilee, followed after, and beheld the sepulchre, and how his body was laid.
56 And they returned, and prepared spices and ointments; and rested the sabbath day according to the commandment.
The verse below writes that Jesus rose on Sunday, the first day of the week, so the day before the first day of the week is Saturday known as the Sabbath:
Luke 24:1-3 King James Version (KJV)
1 Now upon the first day of the week, very early in the morning, they came unto the sepulchre, bringing the spices which they had prepared, and certain others with them.
2 And they found the stone rolled away from the sepulchre.
3 And they entered in, and found not the body of the Lord Jesus.