All perfect praise be to Allah, The Lord of The Worlds, and may His Peace and Blessings be upon our Prophet Muhammad and upon all of his family and companions.
Sending blessings upon the Prophet (Blessings and peace be upon him) is one of the greatest acts of worship encouraged in Islam. Allah the Almighty Says
{What means}: "God and His angels send blessings on the Prophet: O ye that believe! Send ye blessings on him, and salute him with all respect." [Al-Ahzab/56].
Many texts of Sharia have indicated the virtue of sending blessings upon the Prophet (Blessings and peace be upon him) and the way to do that. However, there is no version a Muslim is obligated to adhere to since all versions, which don`t violate Sharia, are permissible.
The version mentioned in the above question doesn`t contradict Sharia, so it is permissible. He letter bi` in " tanhalu bihil ‘uqodu" {By him knots are untied} is causative .i.e. " tanhalu bisababihil ‘uqodu" {Knots are untied because of him} and this matter is beyond dispute. Because of him the greatest knots {Kufur (disbelief) and shirk (polytheism)} of worldly life are untied and the greatest knots will be untied in the Hereafter on the Day of Judgment by virtue of his intercession.
Moreover, according to our school of thought (Shafie), what is stated in the reliable books of the majority of the Maliki, Hanafie, and Hanbali scholars, it is permissible to seek intercession by virtue and person of the Prophet (Blessings and peace be upon him). This is because his status before Allah is established in the Quran and the Sunnah. Seeking his intercession has been mentioned in a special narration where ‘Uthman b. Hunaif told that a blind man came to the Prophet and asked him to pray to God to cure him. He replied: “If you wish, I shall make supplication to God, but if you wish you will endure, for that is better for you." The man asked him to make supplication. ‘Uthman Ibn Haneef (What means) said: "He then commanded him to perform ablution, doing it well, and make this supplication, “O God, I make request of Thee and I turn towards Thee by means of Thy prophet Muhammad, the prophet of mercy. Tirmidhi transmitted it. And Allah the Almighty Knows Best.