Isaiah 56:6 (NET):
As for foreigners who become followers of the Lord and serve him,
who love the name of the Lord and want to be his servants —
all who observe the Sabbath and do not defile it,
Acts 13:42-48 (ESV)
42 As they went out, the people begged that these things might be told them the next Sabbath. 43 And after the meeting of the synagogue broke up, many Jews and devout converts to ...