Allah SWT says which means:
“And We have not sent you (Muhammad) but to be a mercy for the worlds.” (Surah Al Anbiyaa: 107)
“As for those who believe in Allah and hold fast to His (religion), Allah will surely admit them to His great mercy (Paradise) and His abundance of bounty. And indeed they are to the straight path (for up) to Him.” (Surat an-Nisaa: 175)
From the two verses of the Qur’an, it can be understood that Allah SWT sent Islam as a mercy to the universe, especially mankind. Islam is a blessing (a gift of God that brings benefits) to mankind because the goal of Islam is for mankind to obtain the pleasure of Allah, to be happy in the world – the hereafter.
The goal of Islam will be achieved if during his lifetime, humans believe in Allah and adhere to His religion (Islam).
Humans who hold fast to Islam, of course, will always be monotheistic (See QS Al Ikhlash: 1-4; Al Anbiyaa: 25; and Al Baqarah: 255).