In one narration the words are: Sayyiduna Hudhayfah (may Allah be pleased with him) said: "As for me, I know that i'tikaf is only valid in a mosque where the congregational prayer is held." The chain of this narration is mursal (with a missing link).
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الصيام / 5027
Hadith Gradingمحدثین:إسناده مرسل
Hadith Takhrij«اخرجه الطبراني فى المعجم الكبير (9509)»