It is narrated from Sayyiduna Ali (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "O Ali!" and in it, it is also mentioned that he (peace and blessings be upon him) said: "Do not do iq'a' between the two prostrations."
Al-Harith al-A'war is not used as evidence, and likewise Layth bin Abi Sulaym; and the hadith of Ibn Abbas and Ibn Umar is sahih (authentic).
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 2742