To be God’s slave is to be free of everything else.
The modern world treats servitude as the opposite of freedom. Every self-help framework, every economic model, every motivational framework is oriented toward liberating the individual from submission. Islam inverts this entirely.
Abd, the Arabic word for servant or slave, is the term used for every prophet. Abraham is called Khalil Allah, but also abd. Muhammad is described as abduhu wa rasuluhu, His servant and His messenger. There is no degradation in the title. There is a structural claim: that the person who submits entirely to the Creator is the only person who cannot be enslaved by anything else.
When you are God’s slave, you are channeling something with no limit. His vitality moves through you. You are at your most vulnerable, your most surrendered, and therefore at your most liberated. You are free of lesser fears: fear of poverty, fear of death, fear of rejection, fear of irrelevance. These are the levers that every system of control uses to bind people. The person who has surrendered them to something above the system is unreachable by the system.
Source: Al-Ghazali, Ihya Ulum al-Din (Revival of the Religious Sciences), Kitab al-Khawd wa’l-Munazara. Ibn Taymiyyah, Majmu’ al-Fatawa, Vol. 10, on the concept of abudiyyah (servitude).