Quran 5:72 – Meaning Of Term Kafir In This Verse
The goal of Qur’an to is to convince these people that they are committing kufr and shirk. Then if they understand this arguments of Qur’an and continue to believe in such things until they die. Then Allah will mark them as kafir and mushrik on the Day of Judgment. That is the implication of the verse. It is a call to stop to the one who is convinced and understood the concept. It is a warning to them.
Because Trinity can be a confusing concept. Christians in time of Prophet PBUH were convinced that Qur’an was the word of God but they thought that Trinity may not be a problem because they thought they were following Tawheed. So Allah made it crystal clear to these Christians that no. It’s not acceptable now that you are convinced of the Prophet (PBUH) being true and the Qur’an being final word of God. Drop the concept of Trinity now or prepare to be branded as kaffirs both in this world (for punishment that comes after every Messenger) and in the Hereafter.