He said, "It will be so. Allah creates whatever He wills. When He decides on something He just says to it, ‘Be!’ and it is. He will teach him the Book and Wisdom, and the Torah and the Injil…" (Surah Al ‘Imran: 45-48)
In the verse, it is heralded that Allah would instruct Jesus (as) about the Injil, the Torah and the "Book." No doubt, this book in question is very important. We come across the same expression in the Surat al-Ma'idah 110:
Remember when Allah said: "‘Isa, son of Maryam, remember My blessing to you and to your mother when I reinforced you with the Purest Spirit so that you could speak to people in the cradle and when you were fully grown; and when I taught you the Book and Wisdom, and the Torah and the Injil; and when you created a bird-shape out of clay by My permission…" (Surat al-Ma'idah: 110)
When we analyse the "Book" in both of the verses, we see that it may indicate the Qur'an. Primarily, there is only one known divine book on the earth apart from the Torah, the Zabur and the Injil. Besides, in another verse in the Qur'an, next to the Torah and the Injil, the word "Book" is used to indicate the Qur'an.
Allah, there is no god but Him, the Living, the Self-Sustaining. He has sent down the Book to you with truth, confirming what has there before it. And He sent down the Torah and the Injil, previously, as guidance for mankind, and He has sent down the Furqan (the Criterion of judgement between right and wrong). (Surah Al ‘Imran: 2-4)
In this case, we may well consider that the third book which will be taught to Jesus (as) will be the Qur'an and we could assume that this will be possible only if he comes to earth at the end of time. Jesus (as) lived 600 years before the revelation of the Qur'an and it is unlikely that he knew the Qur'an before it was revealed. In this case, that he will learn the Qur'an during his second sojourn on earth could be a reasonable explanation.
This is also explained in a hadith(singular of ahadith):
Abu Hurairah (ra) narrated that Allah's Messenger, peace be upon him, said, "By the One in Whose hand is my self, definitely the son of Maryam will soon descend among you as a just judge, and he will break the cross, kill the pig and abolish the jizyah, and wealth will be so abundant that no one will accept it, until a single prostration will be better than the world and everything in it. (Sahih al-Bukhari)
The ‘ulama (Islamic scholars) say that the meaning in this hadith of his acting as a just judge/ruler is that he will judge by the shari’ah of Islam, i.e. by the judgements in the Book of Allah, the Qur’an, and in the Sunnah of the Last Messenger of Allah, Muhammad, may Allah bless him and grant him peace. Allah surely knows best.
As seen, verses on Jesus' (as) return to the earth are very explicit and remarkable. No similar statements are made for any other prophet mentioned in the Qur'an. Furthermore, no other prophet is referred to as "a Sign of the Hour" and no statement used for any other prophet in the Qur'an includes any connotation implying their return to the earth. However, all these statements are used for Jesus (as). The meaning of this is very clear.