The word(s) "effectual" appears 2 time(s) in 2 verse(s) in Quran in Muhammad Habib Shakir translation.

(1) These are they of whom Allah knows what is in their hearts; therefore turn aside from them and admonish them, and speak to them effectual words concerning themselves.

(سورة النساء, An-Nisaa, Chapter #4, Verse #63)
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(2) This is Allah's guidance, He guides thereby whom He pleases of His servants; and if they had set up others (with Him), certainly what they did would have become ineffectual for them.

(سورة الأنعام, Al-An'aam, Chapter #6, Verse #88)
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