The man made title of Khayru-l-Khalq (Best of Creation) for Prophet Muhammad was invented through the Hadiths in order to worship him and get his intercession on the Day of Judgment.
THE WHOLE UNIVERSE WAS CREATED FOR PROPHET MUHAMMAD (SALAFI AQEEDAH)
Narrated by Umar bin al-Khattab Allah’s Messenger (Peace Be Upon Him) said:
When Adam committed the error, he submitted (to Allah): O Lord, I beg You to forgive me through the mediation of Muhammad. Then Allah said: O Adam! How did you recognize Muhammad as I have not created him yet? He replied: O Lord, when You created me with Your divine hand and breathed Your soul into me, I raised my head and saw ‘la ilaha illallahu Muhammad-ur-rasulullah (“There is no god but Allah, Muhammad is Allah’s Messenger”)’ inscribed on each pillar of the Throne. I discovered that with Your name, the name of only such a person can be associated who is YOUR MOST BELOVED OF ALL THE CREATURES. At this Allah said: O Adam, you have said it correctly. Of all the creatures I love him the most. Now when you offered your prayer through his mediation, I forgave you. And if Muhammad were not there, I would not have created even you.
Tabarani Mu’jam Al-Ausat Volume 006, Page No. 313-314, Hadith Number 6502