Taking Wasila of the Holy Prophet (Sallallahu alaihi wa sallam)
Praying through the Holy Prophet (Sallallahu alaihi wa sallam) i.e. through His Wasila and requesting Him for help is the strongest way to Maghfirah and to get our wishes fulfilled. As given in Shifa As Saqam by Allama Taqiuddin Subki, Pg No. 37.
The Wasila of the Holy Prophet (Sallallahu alaihi wa sallam) before His birth, in His earthly life and after it is well established by the canonic sources of Islam (Nusus). The incidents of the Companions, their successors (Tabi'een) and their successors (Tabe' Tabi'een), the Imams and the Muhaddithin (Hadith experts) are witness to it. As given in Fatawa Ramli, Pg No. 382 and in Fatawa Jamia Nizamia, Pg No. 447.
The People of the Book (Ahle Kitab) would pray through His Wasila before His birth and would be granted victory over their enemies. As given in the Holy Quran:
And when there comes to them a Book from Allah, confirming what is with them. ―although from of old they had prayed for victory against those without faith. Surah Baqarah (2:89)
Even Hadhrat Adam (Peace be upon him) prayed with the Wasila of the Holy Prophet (Sallallahu alaihi wa sallam). This is mentioned indirectly in the Holy Quran and directly in Hadith respectively. It is given in the Holy Quran:
Then learnt Adam from his Lord words of inspiration and his Lord turned toward him; for He is Oft-Returning Most Merciful. Surah Baqarah (2:37)
About the aforementioned words which were taught to Hadhrat Adam (Peace be upon him) and Allah Ta'ala accepted His Tauba (repentance), a Hadith is given in the following books: