Mark 9:2

ἀναφέρει with accusative of person = to lead, a usage unknown to the Greeks. So in Mt.; Lk. avoids the expression. κατʼ ἰδίαν μόνους, apart alone, a pleonasm, yet μόνους, in Mk. only, is not superfluous. It emphasises the κατʼ ἰδίαν, and expresses the passion for solitude. Strictly, it refers only to the three disciples as opposed to the nine, but it really reflects the feeling of Jesus, His desire to be alone with three select companions for a season.