Isaiah 58:13-14 (ESV)
13 “If you turn back your foot from the Sabbath,
from doing your pleasure[a] on my holy day,
and call the Sabbath a delight
and the holy day of the Lord honorable;
if you honor it, not going your own ways,
or seeking your own pleasure,[b] or talking idly;[c]

14 then you shall take delight in the Lord,
and I will make you ride on the heights of the earth;[d]
I will feed you with the heritage of Jacob your father,
for the mouth of the Lord has spoken.”

1 Corinthians 9:19 (ESV)
19 For though I am free from all, I have made myself a servant to all, that I might win more of them.