The Prophet ﷺ said: “The most beloved of your names to Allah are ʿAbd Allah and ʿAbd al-Rahman” (Muslim 2132), and scholars add to them all names formed on a name of Allah. The name al-Wahid occurs 22 times in the Quran; its page in the 99 Names section gives its meaning and verses.
ʿAbd al-Wahid joins ʿabd with al-Wahid, from the root w-h-d of oneness, that of tawhid: the One without partner or equal. The Quran: “Your God is one God” (2:163). The name is written Abdelwahed in the Maghreb and Abdülvahit in Turkey.
Or were you witnesses when death approached Jacob, when he said to his sons, "What will you worship after me?" They said, "We will worship your God and the God of your fathers, Abraham and Ishmael and Isaac - one God. And we are Muslims [in submission] to Him."
