But whoever kills a believer intentionally - his recompense is Hell, wherein he will abide eternally, and Allah has become angry with him and has cursed him and has prepared for him a great punishment. -- Qur'an 4:93
O you who have believed, prescribed for you is legal retribution for those murdered ... -- Qur'an 2:178
Thus, sharia literally includes killing a believer intentionally, which raises the question as how this fits in with Qur'an 4:93.
Question: How is Qur'an 4:93 compatible with the death penalty?
The only way to reconcile this I can think of is that the scope of Qur'an 4:93 is limited to murder (unjust killing) of a believer. If that's correct, I'd like an authoritative reference to back up this guess.
A tafsir indicates Qur'an 4:93 was revealed in light of Miqyas Ibn Sababah whose brother was murdered; the murderer could not be found, so Miqyas killed an emissary sent by the Prophet. (The Prophet subsequently sentenced Miqyas to death, but regarded him as having left Islam.) This is consistent with the idea that the scope of Qur'an 4:93 is limited to murder.