Had spoken (ειρηκε). Past perfect of ειπον (ερω). The disciples had misunderstood Christ's metaphor for death.

That he spake (οτ λεγε). Present active indicative retained in indirect discourse after the secondary tense (εδοξαν).

Of taking rest in sleep (περ της κοιμησεως του υπου). Only use of κοιμησις (from κοιμαω) in the N.T., but it also was used of death (Sirach 46:19). Hυπνου (in sleep) is objective genitive of υπνος (sleep, Matthew 1:24).