Sunan Abi Dawud 1489
سنن أبي داود#1489SahihNarrated Abdullah ibn Abbas: Ikrimah quoted Ibn Abbas as saying: When asking for something you should raise your hands opposite to your shoulders; when asking for forgiveness you should point with one finger; and when making an earnest supplication you should spread out both your hands
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Al-AlbaniSahih
Muhammad Muhyi Al-Din Abdul HamidSahih
Shuaib Al ArnautSahih Muquf
Zubair Ali ZaiHasan
In-book reference: 8:74