I speak from the traditional knowledge in Islam and the knowledge of the saints of Islam.
Muhammad (peace be upon him and his family) said the desire to see God was his embarkation. He also said the remembrance of God lightened his solitude.
But that was the word of a teacher. Muhammad saw God, and ejoyed vision of God, just as Ali said he was not worshipping a god he did not see.
Because of Muhammad, God Almighty had beforehand taken a covenant from all the 124 000 prophets (among whom Jesus, Moses, David, Solomon, Abraham, Noah, Adam, etc...). The Qur'an (which is the word of God, not that of Muhammad) says:
"Behold! Allah (God) took the covenant of the prophets, saying: "I give you a Book and Wisdom; then comes to you an apostle, confirming what is with you; do ye believe in him and render him help."
The prophets agreed to that. Then God asked them if they agreed to Muhammad being the best of them and the beloved of God, and they agreed, as the Qur'an says:
"Allah (God) said: Do ye agree, and take this my Covenant as binding on you? They said: we agree."
Then God said: "Then bear witness, and I am with you among the witnesses." (that Muhammad is the beloved of God and the king of the prophets)
Then God goes on: " If any turn back after this, they are perverted transgressors."
The complete Verses:
"Behold! Allah (God) took the covenant of the prophets, saying: "I give you a Book and Wisdom; then comes to you an apostle, confirming what is with you; do ye believe in him and render him help." Allah said: "Do ye agree, and take this my Covenant as binding on you?" They said: "We agree." He said: then bear witness, and I am with you among the witnesses. If any turn back after this, they are perverted transgressors." (Surah 3, V 81-82)