Sayyiduna Ibn Abbas (may Allah be pleased with them both) said: When "Bismillahir-Rahmanir-Rahim (In the name of Allah, the Most Gracious, the Most Merciful)" was revealed to the Messenger of Allah (peace and blessings be upon him), he (peace and blessings be upon him) knew that the surah had ended, and he (peace and blessings be upon him) turned to the next surah.
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 12492