Wahi – Divine Inspirations and Revelations
Prophet Muhammad ﷺ was not dependent on Angel Jibraeel (Gabriel) (a.s) for all his communication with Allah ﷻ. Prophet Muhammad ﷺ communicated directly with Allah ﷻ as well, many times and without any intermediary whatsoever. For instance during the most famous incident of Isra Wa’al Mira’j (Night Journey & Ascension) he was taken up to the heavens and brought in the direct presence of Allah ﷻ which no other prophet or messenger has ever experienced. In fact, there is a narration from the Prophet ﷺ that: “I have a moment with God in which no angel drawn near or prophet sent, rivals me.” However, the decision to reveal knowledge through angels or directly was decision of Allah ﷻ.
Allah ﷻ communicated with our beloved Prophet ﷺ usually in the late hours of night sometimes through the medium of dreams and sometimes during his deep immersion while in prayer. Prophetic dreams are also part of Prophethood and revelation as explained earlier in Dreams - Part of Prophethood. The heavenly guidance that Prophet ﷺ received was also through the dreams and other means which is preserved for us in authentic hadith literature. This knowledge is secondary to the Quran, which is primary due to pure divine speech of Allah. There is a prophetic hadith that mentions prophet experiencing vision of Allah ﷻ which provided him gilmpse of the unseen and resulted in revelation of knowledge. This happened when he was overtaken by sleep while performing the tahajjud (late night prayer):
“My Lord, Blessed is He and Most High, came to me in the best of appearances. So he said: 'O Muhammad!' I said: 'Here I am O my Lord! And I am at Your service.' He said: 'What is it that the most exalted group busy themselves with?' I said: '[Lord] I do not know.' So He placed His Hand between my shoulders, until I sensed its coolness between my breast, so I knew what was in between the east and the west. He said: 'O Muhammad!' I said: 'Here I am O my Lord! And I am at Your service.' He said: 'What is it that the high ranking angels are discussing?' I said: 'In the acts that raise ranks and the acts that expiate sins, which are walking to the masjid to attend congregation salah, Isbagh Al-Wudu (perfecting ablution) in difficulties, and awaiting the next Salah after the Salah. Feeding others, talking gently and praying while people are asleep. And whoever preserves them, he shall live in goodness and die upon goodness, and his sins shall be like that on the day upon which his mother bore him (without sins as a child is born pure and sinless).'”
The Prophet himself never missed tahajjud and he encouraged the believers to adopt this practice due to the spiritual proximity that we can experience with Allah ﷻ at that time. Abu Hurayra (radiAllahu anhu) reported that the Messenger of Allah ﷺ, said, "Our Lord, the Blessed and Exalted, descends to the lowest heaven every night when a third of the night remains. He says, 'Who is calling on Me so that I can answer him? Who is asking Me for something so that I can give to him? "Who is asking Me for forgiveness so that I can forgive him?'"
 Recorded in Kashfal Asraar (Unveiling of the mysteries) Surah Fatiha – Sufi Tafsir of the Quran by Rashid Al Din Maybudi, a 12 century CE Persian Sunni Scholar and mystic.
 Jami Tirmidhi - Vol. 5, Book 44, Hadith 3234 – Sunnah.com
 Adab Al-Mufrad