In one narration the wording is: Whenever the Prophet (peace and blessings be upon him) mentioned Sayyidah Khadijah (may Allah be pleased with her), he would always praise her and pray for her forgiveness. He would say: "She was granted children by me, while you have been deprived of children by me." Sayyidah Aishah (may Allah be pleased with her) says: The Prophet (peace and blessings be upon him) kept mentioning this for a month.
Al-Tabarani recorded it, and its chain is hasan (good).
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب المناقب / 15280
Hadith Gradingمحدثین:إسنادہ حسن۔
Hadith Takhrij«اخرجه الطبراني فى المعجم الكبير (13/23)»