He spoke in sure and certain terms to the disbelievers, saying he would never join them

although the disbelievers were far stronger and in greater numbers at that time, the prophet (saas) paid no heed to their disposition and threats, but with great determination preached the words of the qur'an and made it quite clear that he would never turn from the true path. determination and patience are defining characteristics of the faithful, and every muslim must take the determination and strong will of the prophet (saas) as a model. some verses on that subject are as follows:

say: "i am forbidden to worship those you call upon besides allah." say: "i do not follow your whims and desires. if i did i would go astray and not be among the guided." say: "i stand on a clear sign from my lord and yet you have denied it. i do not have in my possession what you are in such haste to bring about. jurisdiction over it belongs to allah alone. he tells the truth and he is the best of deciders." (surat al-an'am: 56-57)

say: "unbelievers! i do not worship what you worship and you do not worship what i worship. nor will i worship what you worship nor will you worship what i worship. you have your religion and i have my religion." (surat al-kafirun: 1-6)
say: 'my people, do as you think best; that is what i am doing.you will soon know…'
(surat az-zumar: 39)