Epistle of Barnabas

Moreover concerning the Sabbath likewise it is written in the Ten Words, in which He spake to Moses face to face on Mount Sinai; And ye shall hallow the Sabbath of the Lord with pure hands and with a pure heart.

Ἔτι οὖν καὶ περὶ τοῦ σαββάτου γέγραπται ἐν τοῖς δέκα λόγοις, ἐν οἷς ἐλάλησεν ἐν τῷ ὄρει Σινᾶ πρὸς Μωϋσῆν κατὰ πρόσωπον: Καὶ ἁγιάσατε τὸ σάββατον κυρίου χερσὶν καθαραῖς καὶ καρδίᾳ καθαρᾷ.

And in another place He saith; If my sons observe the Sabbath then I will bestow My mercy upon them.

καὶ ἐν ἑτέρῳ λέγει: Ἐὰν φυλάξωσιν οἱ υἱοί μου τὸ σάββατον, τότε ἐπιθήσω τὸ ἔλεός μου ἐπ̓ αὐτούς.