The above hadith is often quoted to emphasis gaining of knowledge other than Islamic knowledge because at that time, China did not have Islam but the hadith says so. I have heard this may not be authentic hadidth. Is this true?
I have heard from our Masjid Imam who was a learned Imam in well educated area that he could not found source of this hadith even though he read many book. Therefore this hadith is not true and can be treated as fabricated.
This link on IslamQA also says this is farbicated hadith. The correct hadith is
‘Seeking knowledge is obligatory upon every Muslim'
There would be two 'matan' or 'the content' of the concerning Hadis or maybe more, I know only two. First one (translated) : Seek knowledge is a fardh(obligation) onto all muslim. The first Hadis is sahih.
Secondly (translated) : Seek knowledge is a fardh(obligation) onto all muslim, seek knowledge even to China .
The second Hadis is false or not sahih.
Al-Hafiz Mizi split the second hadis into two part, he wrote it as the first part 'Seek knowledge is a fardh(obligation) onto all muslim' is sahih, but the second part 'seek knowledge even to China' is not sahih because there is no root to support of it's authenticity or even to prove it's base of existence.
There is no chain of narrator for the second hadis, as far as Al-Hafiz Mizi prescribed but the first Hadis is sahih. People always mistaking as the misunderstood what Al-Hafiz Mizi mean by saying that part of the hadis is right so the hadis is acceptable, its the firs't only.
The mentioned hadith can be found in Kanz al-Ummal , No 28697: The Prophet (SAWA) said,
Seek knowledge even in China, for verily to seek knowledge is an obligation on every Muslim.
Seeking knowledge is therefore not restricted on seeking Islamic knowledge, but knowledge in general when it is useful for the development and advancement of a Muslim himself and its community.