According to both Islamic sources and the intellect, God cannot be seen by the physical eye neither in this life nor in the next. However He can be seen through the eyes of the heart. Up to each given individual’s capacity, after purifying their souls, and engaging in prayers and religious self discipline, their hearts can see and feel Him through a type of inner witnessing.
If what we mean by seeing God is seeing Him through the outer physical eye, it something totally ruled out both by the intellect and Islamic sources.
The intellect: the action of seeing takes place only when things are exposed to light beams and their reflection is captured by the eye. This means that there should firstly be an external thing present and secondly it should be captured by the eye in the field of vision. Based on this we cannot see things which are behind us, whereas God is not a physical entity and He does not have the physical features of a physical being. Therefore He can not be seen with the naked eye.
Islamic sources: There are verses in the Holy Quran and traditions which stipulate the impossibility of seeing God.
a) The Holy Quran says:
1 - O Moses you can never see me.
2 – The eyes cannot see Him.
b) Traditions: "God never appears before the eyes"
"The eyes have never seen you" and “The eyes will never see him openly”
But if what we mean by seeing God is seeing Him through an inner witnessing and witnessing the light of the names and attributes of God in the heart, within the limits that human beings have then it is possible. Imam Ali (a) says: "Hearts can perceive Him". In another tradition he says to Za'lab: "Shame on you! Eyes cannot see Him but the hearts can."