Thou hast received and heard (εἴληφας καὶ ἤκουσας)
The former of these verbs is in the perfect tense: thou hast received the truth as a permanent deposit. It remains with thee whether thou regardest it or not. The latter verb is ill the aorist tense, didst hear (so Rev.), denoting merely the act of hearing when it took place.
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See on Rev 3:2.
On thee
Omit.
As a thief (ὡς κλέπτης)
Thief, as distinguished from hp λῃστής robber, a plunderer on a larger scale, who secures his booty not by stealth, but by violence. Hence the word is appropriate here to mark the unexpected and stealthy coming of the Lord. Compare 1Th 5:2, 1Th 5:4; 2Pe 3:10.
Thou shalt not know what hour l will come upon thee
The Greek proverb says that the feet of the avenging deities are shod with wool. The sentiment is voiced in the two following fragments from Aeschylus: