It is narrated from Sayyiduna Salman al-Farsi (may Allah be pleased with him), he said: I read in the Torah that performing wudu after eating (not the ritual ablution, but rather washing the hands and rinsing the mouth) is a cause of blessing. I mentioned this to the Noble Prophet (peace and blessings be upon him), so the Messenger of Allah (peace and blessings be upon him) said: "Performing wudu before eating and after eating is a cause of blessing." This hadith is known only through the narration of Qais ibn Rabi', and he is weak in hadith.
Hadith Referenceشمائل ترمذي / باب ما جاء فى صفة وضوء رسول الله صلى الله عليه وسلم عند الطعام / 186
Hadith Gradingزبیر علی زئی:سنده ضعيف
Hadith Takhrij{ «سنده ضعيف» } : «سنن ترمذي: 1846. وقال: وقيس يضعف فى الحديث . سنن ابي داود : 3761 وقال ابوداود: وهو ضعيف .» اس روایت کا راوی قیس بن الربیع جمہور محدثین کے نزدیک بُرے حافظے کی وجہ سے ضعیف تھا ، لہٰذا یہ سند ضعیف ہے ۔ نیز دیکھئے : [ انوار الصحيفه ص 123 ]