All praise and thanks are due to Allah, and peace and blessings be upon His Messenger.
"The Holy Spirit in quran refers to the Angel Jibreel (Gabriel), also known as Jibraaeel; he is the message-bearer par excellence from Allah, the Lord of Glory and Grace; he is also the conduit of divine support and assistance bestowed on Prophets, Messengers as well as righteous people who strive in the path of Allah.
1. Thus we read in the Qur’an that the Prophets (peace be upon them all) are chosen by Allah by sending down the Holy Spirit with the revelations: “He sends down the Spirit from His command, upon those of His servants He chooses, in order to warn people of the Day of Meeting.” (Ghafir: 15)
2. We also read in the Qur’an that it (the Qur’an) was sent down upon the Prophet (peace and blessings be upon him) through the medium of Holy Spirit: “Say: The Holy Spirit brought it down from your Lord with the truth, to strengthen those who believe, and as a guidance and good tidings to the Muslims.”(An-Nahl: 102)
"And your Lord, He is indeed the August, the Compassionate. And it is a sending down from the Lord of the Worlds, brought down by the Trustworthy Spirit, upon your heart, that you may be one of the warners, in Arabic speech.” (Ash-Shu`ara': 191-195)
3. It is in the same spirit that we read in the Qur’an that the Holy Spirit was sent down to strengthen Jesus and assist him in his work:
“We gave Jesus, son of Mary, clear signs, and strengthened him with the Holy Spirit…” (Al-Baqarah: 253)
“Then Allah will say, O Jesus son of Mary! Remember My favor upon you and upon your mother; how I strengthened you with the Holy Spirit…” (Al-Ma'idah: 110)
4. Furthermore, we read in the Prophetic traditions: The Prophet (peace and blessings be upon him) said, “Verily, the Holy Spirit has cast this idea in my heart: No soul shall die before its appointed time and without having exhausted the means of livelihood apportioned for it, so try to look for a livelihood as best as you can, but don’t seek it through unlawful means.”(Reported by Abu Nu`aym in Hilyah)
The Prophet (peace and blessings be upon him) prayed to Allah to strengthen the famous poet Hassan ibn Thabit with the Holy Spirit in composing poems in defense of Islam: “O Allah! Strengthen him with the Holy Spirit.” (Reported by al-Bukhari)
The Prophet (peace and blessings be upon him) later on said about Hassan: “Verily Allah, the Glorious and Mighty, is strengthening Hassan with the Holy Spirit.” (Reported by at-Tirmidhi and Ahmad) “The Holy Spirit is with Hassan in his work!” (Reported by Abu Dawud)
It should be clear from the above that the Holy Spirit is the Angel Jibreel sent by Allah to assist His chosen servants in their divinely ordained missions."
And Allah knows best.