Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) said: A man asked the Prophet (peace and blessings be upon him) about something concerning the prayer, and the Prophet (peace and blessings be upon him) said: "Pass (water) between the fingers of your hands and your feet." The narrator said: This means: perform ablution thoroughly. Among what the Prophet (peace and blessings be upon him) said to that man was also this: "When you bow, place your palms on your knees until you are at rest (here the narrator is unsure about one word), and when you prostrate, place your forehead firmly on the ground until you feel the firmness of the ground." (Allamah al-Haythami says:) I say: Imam al-Tirmidhi recorded the part of this narration about passing water between the fingers.
Imam Ahmad recorded it; its chain contains Abd al-Rahman bin Abi al-Zinad, who is da'if (weak).
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الصلاة / 2792