Read this: The Ming dynasty granted titles to lamas of schools such as the Karmapa Kargyu, but the latter had previously declined Mongol invitations to receive titles. When the Ming Yongle Emperor invited Je Tsongkhapa (13571419), founder of the Gelug school, to come to the Ming court and pay tribute, the latter declined. Wang and Nyima write that this was due to old age and physical weakness, and also because of efforts being made to build three major monasteries. Chen Qingying states that Tsongkhapa wrote a letter to decline the Emperor's invitation, and in this reply, Tsongkhapa wrote:
Now answer this question, if there is an answer (If it cannot be answered, return "unanswerable"): Who wrote the letter declining the Emperor's invitation?
Tsongkhapa