Korah and 250 leaders rebelled against Moses and Aaron, God detested and rejected them, and made the earth cleft asunder and swallow the rebels.
1) Can I use one word to convey the meaning of "detest and reject"? Do "shun" and "spurn" work?
2) Or does the word "reject" itself here already contain the meaning of "detest"?
"Reject" is similar to "detest" but definitely not synonymous. Rejection is usually a result of detesting someone and not the other way round. So, no. You would need both words.
reject verb
to refuse to accept, use or believe something or someone
Source: Cambridge Dictionaries Online
If you choose to use "shun", note that it means rejection in the sense of ignoring someone and not refusing to accept them.
shun verb
to ignore someone and not speak to that person because you cannot accept their behaviour, beliefs, etc.
Source: Cambridge Dictionaries Online
"Spurn" meanwhile is the other meaning of "reject":
spurn verb
to refuse to accept something or someone because you feel that thing or person is not worth having
Source: Cambridge Dictionaries Online
Thus, neither "shun" nor "spurn" carry the meaning of both "reject" and "detest".
Can it be condemn?
Express strong disapproval of.
Declare or judge unfit for use or habitation.
Difficult indeed. Despise ? 1. To regard with contempt or scorn: despised all cowards and flatterers. 2. To dislike intensely; loathe: despised the frigid weather in January.
One word that conveys both detestation (i.e. some sense of unfavourable judgment) and rejection is deprecate, which in its most common uses indicates a kind of reasoned dislike: ‘to express earnest disapproval of; to urge reasons against; protest against’. The implied element of reasoned distaste brings us close to the sense of ‘detest’ (although ‘detest’ can also indicate a less rational reflex).
‘Deprecate’ can therefore also connote a consequential rejection: if you deprecate something, you don’t merely happen to favour a different option: in effect you argue that people should not only avoid doing or using this thing, but also reject it even as an option.
One well-established such usage was in the World Wide Web Consortium’s terminology for evolving standards for HTML4, where ‘deprecated’ indicates code elements that have been superseded and should be avoided. In using this term, the W3C effectively communicates disapproval while still recommending support for those who insist on using the outdated code. (For context, the next stage is ‘obsolete’: at that point, judgment and choice becomes irrelevant.)
