According to the majority of jurists, scholars of Hadith and Muslim philosophers, the journey of Al-Israa’ and Al-Mi`raj was in both body and soul. Therein lay its being a miracle. There is much evidence of this point.
the eminent scholar Sheikh `Atiyyah Saqr, former head of Al-Azhar Fatwa Committee, states:

Scholars have differed as to whether the Prophet’s journey of Al-Israa’ and Al-Mi`raj was in soul only or in both body and soul.
the majority of jurists, scholars of Hadith, and Muslim philosophers agreed that it was in both body and soul for many reasons.
First, according to Almighty Allah’s words: (Glorified be He Who carried His servant by night from theInviolable Place of Worship to the Far Distant Place of Worship.) (Al-Israa’ 17: 1), He Almighty has referred to the Prophet (peace and blessings be upon him) as “His servant.” The word “servant” does not refer to one’s soul only; it refers to the servant as a whole, body and soul.
this is similar to the word “slave” in Allah’s words: (Hast thou seen him who dissuadeth a slave when he prayeth?) (Al-`Alaq 96: 9) and (And when the slave of Allah stood up in prayer to Him, they crowded on him, almost stifling.) (Al-Jinn 72: 19) The word “slave” in both these verses refers to the person in question as a whole, body and soul.

Second, had the Prophet’s journey of Al-Israa’ and Al-Mi`raj been in soul only, it would not have been regarded as a miracle. It would have been then an ordinary dream. While sleeping, many people visit remote places and see extraordinary things without moving an inch from the places they are already in, and there is nothing extraordinary about that to other people.
had the Prophet’s journey of Al-Israa’ and Al-Mi`raj been a dream, Allah Almighty would not have mentioned it in the Qur’an in terms that express its being a miracle and extraordinary incident.
third, Allah Almighty says about the journey of Al-Israa’ and Al-Mi`raj: (We appointed the vision which We showed thee as an ordeal for mankind.) (Al-Israa’ 17: 60). “Ordeal” here refers to its being a trial.

Contemplating this, the journey would not be a trial unless it was in both body and soul. Had it been in soul only, there would not have been a trial or something extraordinary regarding it.
Besides, when the unbelievers knew about the journey of Al-Israa’ and Al-Mi`raj, they wondered how the Prophet (peace and blessings be upon him) could make it on one night, when they would make a similar journey in a month. [Why should they disbelieve it, if it were a mere dream?]
Fourth, it was Allah Almighty Who made His Prophet (peace and blessings be upon him) have that journey, and, certainly, nothing is impossible for Allah Almighty to do; He Almighty is able to do all things. Hence, there is nothing that calls us to doubt the occurrence of the journey in both body and soul.
those who say that the journey was in soul only cite as evidence for their view the Qur’anic verse: (We appointed the vision which We showed thee as an ordeal for mankind.) (Al-Israa’ 17: 60).

they believe that the vision (ru’ya) here refers to a dream, not to an actual seeing.
But this opinion is not wholly tenable, for ru’ya, lexically speaking, refers also to seeing with the eyes. Besides, according to Al-Bukhari, Ibn `Abbas (may Allah be pleased with him) said, commenting on the verse in question, “The sights which the Prophet (peace and blessings be upon him) was shown on the Night Journey when he was taken to Jerusalem were actual sights, (not dreams).”
those who are of the opinion that the journey was in soul only also cite as evidence for their view the Mother of the Believers `A’ishah’s hadith: “The Prophet’s sanctified body was not missing on the Night Journey.’
But this point is also refuted for the following reasons.
1. The hadith reported to have been said by `A’ishah is not an authentic one; there are missing and unknown reporters in its chain of narration.
2. `A’ishah (may Allah be pleased with her) was not yet married to the Prophet (peace and blessings be upon him) at the time of the journey. She might even not have been born then, if we take into account the controversy regarding the date of Al-Israa’ and Al-Mi`raj.
3. Her saying: “The Prophet (peace and blessings be upon him) did not see his Almighty Allah with his eye” indicates that she believed that the journey was in both body and soul. Had she thought that it was in soul only, she would not have said that.
4. Since the hadith ”The Prophet’s sanctified body was not missing” is not authentic, there is no need to attempt to explain it to mean that the journey was in both body and soul, for some say that the hadith indicates that his soul was not separated from his body.

Anyway, what we are required to believe with regard to Al-Israa’ and Al-Mi`raj is that it did take place, as Allah Almighty tells us in the Glorious Qur’an.

As for its being in soul only or in both body and soul, this is a controversial point that needs not to be tackled strictly. One can adopt either view, but one is to bear in mind at the same time that Allah Almighty is able to do everything and that the Prophets’ visions, according to scholarly agreement, are true.