Mujahid (may Allah have mercy on him) said: I received an invitation and was told, "We invite you to participate in the completion of the Qur'an, because we have heard that supplication is accepted at the time of completing the Qur'an," and they made supplications.
Hadith Referenceسنن دارمي / من كتاب فضائل القرآن / 3514
Hadith Takhrijاس اثر کی سند صحیح ہے۔ حکم: ابن عتبہ ہیں۔ دیکھئے: [ابن الضريس فى فضائل القرآن 49، 81] ، [أبوعبيد، ص: 107] ، [ابن أبى شيبه 10089] ، [شعب الإيمان 2072]