Abu al-Abbas (may Allah have mercy on him) narrated it and mentioned it, saying: (They were) Hawazin, but he did not mention the word 'qulu' (say). A group narrated it in this way from Muhammad bin Ubayd, and so it is in our copy of the book of Abu Dawud. Abu Sulayman al-Khattabi (may Allah have mercy on him) used to read it as: 'I saw the Messenger of Allah (peace and blessings be upon him) tawaka', and he explained that 'tawaka' means exerting oneself when raising and stretching out the hands in supplication.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب صلاة الاستسقاء / 6438