التفسير التبليغي
(وَوَجَدَكَ ضَالًّا فَهَدَى)
Meaning, He raised you to the position of messengership and conveying the message.
Meaning, you were perplexed in choosing a way of life, so He guided you to the effort of religion.
(وَوَجَدَكَ ضَالًّا فَهَدَى) is evidence of Allah's guidance that illuminates the path after bewilderment.
(وَوَجَدَكَ ضَالًّا) in the past, from what you are upon today of various forms of guidance and types of blessings.
(وَوَجَدَكَ ضَالًّا فَهَدَى) He found you not knowing the effort of truth, so He guided you to it.
(وَوَجَدَكَ ضَالًّا فَهَدَى) from what you were upon regarding the matter of prophethood and the Sharia, so He guided you to both of them.
(وَوَجَدَكَ ضَالًّا): from the legislation (فَهَدَى).
(وَوَجَدَكَ ضَالًّا فَهَدَى), meaning: on a path other than this religion with which you were sent. And he (peace be upon him) was not in the misguidance of the disbelievers nor in their heedlessness, because he never committed polytheism. Rather, he was seeking guidance from his Lord, the Mighty and Majestic, and was a monotheist.
Bewilderment had overcome him (peace be upon him), and the search for the path of salvation and deliverance exhausted him, so Allah guided him and made him a lamp of guidance for all worlds.
The most honorable thing He bestowed upon him was guidance.
(وَوَجَدَكَ ضَالًّا فَهَدَى) Among the strange and excellent interpretations is that the Arabs, when they found a solitary tree in a barren land with no other trees around it, called it a "ḍāllah" (lost one), and they would be guided by it on the path. So Allah Almighty said to His Prophet: (وَوَجَدَكَ ضَالًّا فَهَدَى) meaning, I found you with no one upon your religion, so I guided creation to Me through you.
Source: التفسير التبليغي