When rising and sitting up between the two prostrations, there are a number of supplications we can make, but the most common one is ربي اغفر لي usually translated as, “My Lord, forgive me.”
The word رب comes from a root that denotes the rectification of things and setting things right. This meaning has evolved to refer to a master, lord, owner or guardian, because they all are in charge of setting right the affairs of those over whom they have responsibility. And Allah is referred to as the ‘rabb’ because he rectifies the condition of His creation.
When we call upon Allah use the term ربي, we are emphasising our relationship to Him - that He is our Master who is in charge of our affairs, and we are His slaves. When we call upon Him saying ربي, we are indicating our obedience to Him and submission to His will. This invocation stirs two profound emotions: an intense hope, love, and longing, recognizing that He alone nurtures and sustains us, caring for our physical and spiritual well-being. Simultaneously, it instills a sense of reverence in our hearts, aware that He is the Sovereign, meriting our complete obedience and surrender.
The term اغفر comes from the root غ ف ر which conveys the notions of covering, hiding, or shielding someone from the repercussions of their errors or wrongdoings. Within the framework of forgiveness, it suggests that the forgiver is not merely overlooking the fault but is also proactively aiming to shield the offender from the adverse outcomes of their deeds, as if these missteps never took place. There's an absence of any form of blame or reproach, even in thought, embodying the purest form of forgiveness.
So when we say ربي اغفر لي we are essentially saying, “My Lord, the overseer of all my matters, to whom I devote myself in total submission and obedience, I implore You to pardon my transgressions, to ignore them, and to consider them as though they never happened.”