It is narrated from Sayyiduna Safwan al-Zuhri (may Allah be pleased with him) that the Prophet (peace and blessings be upon him) said: "Whoever prays four rak'ahs before Zuhr, for him is a reward equal to the reward of freeing a slave," or he said: "equal to freeing four slaves from the descendants of Isma'il (peace be upon him)."
Imam al-Tabarani (may Allah have mercy on him) said: "This hadith is narrated from Safwan al-Zuhri (may Allah be pleased with him) only with this chain, and Zayd bin Akhzam (may Allah have mercy on him) is alone in narrating it."
Hadith Referenceالمعجم الأوسط / باب الميم / 6052
Hadith Gradingمحدثین:فيه جماعة لم يُترجموا
Hadith Takhrij«قال الهيثمي: فيه جماعة لم أجد من ترجمهم «مجمع الزوائد ومنبع الفوائد، ج 2، ص 220»» «أخرجه ابن حجر فى «المطالب العالية» برقم: 616 / 2»