In a number of places certain verbs are cited in Perschbacher's "The New Analytical Greek Lexicon" which do not have any tense or voice directly stated.
In almost all of these cases, one can assume that the tense is Present and the voice is Active, especially when the sense is that of a command (Imperative).
The imperative mood corresponds to the English imperative, and expresses a command to the hearer to perform a certain action by the order and authority of the one commanding. Thus, Jesus' phrase, "Repent ye, and believe the gospel" (Mk.1:15) is not at all an "invitation," but an absolute command requiring full obedience on the part of all hearers.
Bibliography Information
Thayer and Smith. "Greek Lexicon entry for ". "The New Testament Greek Lexicon". <http://www.searchgodsword.org/lex/grk/view.cgi?number=5773>.