Indeed, the dearest of your names to Allah is ‘Abdullah and ‘Abdur-Rahmān

Al-Qurtubi said: Names similar to these two, such as ‘Abdur-Rahīm, ‘Abdul-Malik, and ‘Abdul-Samad, are also included. These names are the most beloved to Allah because they combine an attribute that is a must for Allah and an attribute that is a must for humans, which is servitude. The slave is then attributed to the Lord in a genuine association, making these names truthful and honored through this composition, thereby attaining this merit. Others said: The rationale behind specifying these two names is that, in the Qur’an, the attribution of '‘Abd' (slave) to any of Allah's names occurs only with these two. Allah Almighty says: {Yet when the slave of Allah stood up supplicating Him}, and in another verse, He says: {The slaves of the Most Compassionate}. This is further supported by His saying: {Say, “Call upon Allah or call upon the Most Compassionate”}.