بِسْمِ اللهِ الرَّحْمٰنِ الرَّحِيْم
Allah has always been one and no one else has ever been (equal or partnering) with Him. Allah is unique in His attributes, actions, and Lordship. He is the Only one who deserves to be worshipped.
The word Al-Waahid occures 22 times in The Qur’an such in Surat Ar-Ra’d 13:16,
وَهُوَ الْوَاحِدُ الْقَهَّارُ
“He is the One, the Supreme and Irresistible.”
The word Al-Ahaad occured once, in Surat Al-Ikhlas 112:1,
قُلْ هُوَ اللَّهُ أَحَدٌ
“Say, ‘He is Allah, the One and Only.’”