Alqamah bin Wa'il bin Hujr (may Allah have mercy on him) narrates from his father (may Allah be pleased with him) that when the Messenger of Allah (peace and blessings be upon him) bowed, he kept his fingers apart, and when he prostrated, he kept them together.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 2695
It is narrated from Sayyiduna al-Bara' bin Azib (may Allah be pleased with him) that when the Messenger of Allah (peace and blessings be upon him) prostrated, he placed his hands on the ground facing the qiblah; his fingers and palms were also facing the qiblah.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 2696
It is narrated from Sayyiduna al-Bara' (may Allah be pleased with him) that the Prophet (peace and blessings be upon him), "when he bowed, would keep his back level, and when he prostrated, would turn his fingers towards the qiblah."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 2697
It is narrated from Sayyiduna Ibn Umar (may Allah be pleased with them both) that it is disliked (makruh) not to keep one's palms facing the qiblah during prostration.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 2698