Tafsir of Al-Ma'idah 5:70

"We have taken a covenant" Their covenant to [uphold] monotheism.

"And We sent to them messengers" To inform them of what they should do and what they should avoid in their religion.

"Whenever there came to them a messenger" A conditional sentence acting as an adjective for "messengers." The referent [pronoun] is omitted; it means: "a messenger from among them."

"With what their souls did not desire" With that which contradicts their whims and opposes their desires, such as the hardships of religious obligations and acting according to the laws.

If you ask: Where is the response to the conditional clause? I say: The statement "a party they denied, and a party they kill" stands in place of the response. This is because a single messenger cannot be two parties, and because it is acceptable to say, "If you honor my brother, you honor your brother." I say: It is omitted, and indicated by his words: "a party they denied, and a party they kill." It is as if it were said: "Whenever a messenger came to them from among them, they showed him hostility."

His words "a party they denied" are an independent response to someone who asks: "How did they treat their messengers?"

If you ask: Why was one of the two verbs brought in the past tense and the other in the present tense? I say: "They kill" (yaqtulun) was brought to narrate a past state, to emphasize the heinousness of the killing, to bring that abominable state to mind, and to express astonishment at it.

"That there would be no trial" It was read as an la yakuna (in the accusative) based on the apparent [grammar], and as an la yakunu (in the nominative) where an is the lightened form of the heavy anna. Its origin was annahu la yakunu fitnah (that there would be no trial), then anna was lightened and the pronoun of the state (damir al-sha'n) was omitted.