Howbeit Jesus spake of his death: but they thought that he had spoken of taking of rest in sleep.
Berean Study Bible (BSB) - John 11:13 >They thought that Jesus was talking about actual sleep, but He was speaking about the death of Lazarus.
Textus Receptus (TR) - John 11:13 >Εἰρήκει δὲ ὁ Ἰησοῦς περὶ τοῦ θανάτου αὐτοῦ· ἐκεῖνοι δὲ ἔδοξαν ὅτι περὶ τῆς κοιμήσεως τοῦ ὕπνου λέγει.