Praise be to Allah, the Lord of the Worlds; and may His blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions.Al-Bukhari reported in his Sahih that Abu Said Al-Khudri, may Allah be pleased with him, narrated that the Prophet (Sallallahu Alaihi wa Sallam) told the companions: "Are you not able to read a third of the Qur'an in one night? They found this very difficult and replied that nobody amongst us can do so. Then the Prophet (Sallallahu Alaihi wa Sallam) said: "Allah, The One, the Self sufficient "Surah Qul Huwa Allahu Ahad equals a third of the Qur'an."
Muslim also reported that Abu Al Darda narrated: "Say, He is Allah, The One, (Surah 112) equals a third of the Qur'an." reported by Al-Thirmidhi, and Al- Albani classified it as an authentic Hadith.
Al-Mubarakpuri stated in Sharh Al-Thirmidhi that it could mean that whoever reads it 3 times is as if he reads the whole Qur'an.
The reading of the above Surah 3 times is also confirmed as part of the remembrance of the morning and of the evening, and when going to sleep, as it is reported in the Hadith: "Reciting Surah Ikhlas, and the two last chapters of the Qur'an in the morning and evening 3 times, will protect you from everything", reported by Abu Dawud and Al-Thirmidhi, and Al-Albani classified it as an authentic Hadith.
Moreover, Al-Bukhari reported that Aisha, ( may Allaah be pleased with her), said that Prophet (Sallallahu Alaihi wa Sallam) when resorted to his bed every night, used to put his hands together, blow onto them and then read : "Surah Ikhlas and the last two chapters (112-113-114), then wipe over his body, he used to start from his head, then his face, then the rest of his body, and he used to do so three times."
Nevertheless, the people of knowledge state that getting the reward mentioned does not serve instead of reading the whole Qur'an. Reading Surah al-Ikhlas repeatedly does not serve instead of reading Al-Fatihah (the opening chapter) in prayer, and reading it 3 times does not serve instead of reading the whole Qur'an for the one who vowed to read the whole Qur'an.
We also remind the questioner that the guidance of our righteous predecessors is that they were not keen on reading Surah Al-Ikhlas 3 times rather they were keen on reading the whole Qur'an.
Allah knows best.