Praise be to Allah, and may peace and blessings be upon the Messenger of Allah. To proceed:
The Noble Qur’an states that Jacob, peace be upon him, advised his children before his death to adhere to monotheism and worship Allah alone. The Qur’an also mentions the Scriptures of Abraham, peace be upon him, in several places. Among the countries with the largest Muslim populations is Indonesia, where Islam spread through contact with Muslim merchants.
The Noble Qur’an explains that when Jacob, peace be upon him, approached the end of his life, he asked his children what they would worship after him. He said to them:
“What will you worship after me?”
They replied:
“They said: We will worship your God and the God of your fathers, Abraham, Ishmael, and Isaac—the One God, and to Him we submit.” [Al-Baqarah: 133]
Thus, Jacob’s advice concerned the greatest foundation: affirming the Oneness of Allah and worshipping Him alone.
The Scriptures of Abraham, peace be upon him, are mentioned in the Noble Qur’an in more than one place. Among them is the following:
Allah, Most High, says in Surah Al-Aʿla:
“The Scriptures of Abraham and Moses.” [Al-Aʿla: 19]
And He, Glorified and Exalted, says in Surah An-Najm:
“Or has he not been informed of what was in the Scriptures of Moses, and Abraham, who fulfilled [his obligations]?” [An-Najm: 36–37]
These are two places where the Qur’an explicitly mentions the Scriptures of Abraham, peace be upon him.
The source states that Indonesia is one of the largest Muslim countries in terms of the number of Muslims in Asia, while Nigeria is among the countries with the largest Muslim populations in Africa.
The source indicates that Islam spread in Indonesia through contact with Hadrami Muslim merchants, with trade and interaction with Muslims playing a role in bringing Islam to the region and spreading it among its people.
It should be noted that asking about the “highest percentage of Muslims” is different from asking about the “largest number of Muslims.” The percentage of a country’s population is not the same as the total number of Muslims. Therefore, the wording of the question is not precise in this respect.
Jacob, peace be upon him, advised his children to uphold monotheism and remain devoted to the worship of Allah alone. The Qur’an mentions the Scriptures of Abraham in Surah Al-Aʿla and Surah An-Najm. As for Indonesia, it is one of the countries with the largest Muslim populations in Asia, and the source states that Islam spread there through contact with Hadrami Muslim merchants.
And Allah knows best.