(a) It is narrated from Sayyiduna Abu Hurayrah (may Allah be pleased with him) that he said: I never saw him (peace and blessings be upon him) in any obligatory or voluntary prayer except that he raised his hands towards the sky and supplicated, and then after that said the takbir.
(b) In a hadith there is that he (peace and blessings be upon him) said: "Whenever one of you begins the prayer, let him raise his hands and keep his palms facing the qiblah."
However, it is weak.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 2320
Hadith Gradingمحدثین:منكر
Hadith Takhrij«منكر۔ اخرجه ابو نعيم في الحلية 9/238»