<B>If you place your cursor over הרו and then right-click your mouse and ask for "Lexical & Grammatical Help" (either "replace" or "new") you will get a list of lexicons and grammars and commentaries where הרו is mentioned. It just so happens that this infinitive is mentioned in Gesenius' and Waltke & O'Connor's grammars as an example of where an infinitive absolute "appears as a substitute for the finite verb."
Below are the relevant sections taken from the Grammars:
Gesenius, Section 113,y:
4. </B>Finally the infinitive absolute sometimes appears as a
substitute for the finite verb, either when it is sufficient simply to mention the verbal idea (see
z), or when the hurried or otherwise excited style intentionally contents itself with this infinitive, in order to bring out the verbal idea in a clearer and more expressive manner (see
aa).
Gesenius, Section 113,ff:
(
e) For any historical tense (like the Latin
historic infinitive) in lively narration (or enumeration) and descriptron, even of what is still taking place in present time, e.g.
Hos 4:2 swearing and breaking faith,
and killing,
and stealing,
and committing adultery (in these they are busied);
10:4 (after a
perfect);
Is 21:5,
59:4,
Jer 8:15,
14:19,
Jb 15:35; cf. further
Jer 32:33,
Ec 4:2.—In
Ez 23:30,
Pr 12:7,
15:22, and
25:4, the infinitive cf. absolute is best rendered by the passive.
Waltke & O'Connor, Page 595:
The infinitive absolute without
waw may serve in place of a finite verb in making emphatic expressions and indignant questions (## 9–11).
55 When the infinitive absolute is used as an interjection the reader must supply the appropriate person and aspect on the basis of semantic pertinence. The distinction between the use of the infinitive as interjection or as an adverbial is somewhat blurred and subjective. For example, in # 11, the infinitives could be rendered as below (or as 'You rely ... You conceive ... '), or they could be interpreted as qualifying adverbials and rendered, 'No one calls for justice ... , relying on empty argument and speaking lies, conceiving trouble and giving birth to evil!'