Yakeen

1 Ilm al-yaqîn (the knowledge of Certainty)
2 Ayn al-yaqîn (the Eye of Certainty)
3 Haqq al-yaqîn (the total reality of Certainty)


Yaqeen  is generally translated as "certainty", and is
considered the summit of the many stations by which the path of walaya
(Sainthood) is fully completed. This is the
repository of liberating experience in Islam. In relation to the
exoteric religious life, Certainty is the sister of religious life in
its perfection (ehsân), that is to say the adoration of Allah
according to the visionary way; through this channel it is the pillar
of Islam in the accomplishment of its external practices, as it is the
foundation of faith (iman) in its internal dogma. It is in fact ihsân
which gives the external religion its true meaning and the domain of
faith its real values. Certainty (al-yaqîn), comprises three degrees.

Ilm al-yaqîn (the knowledge of Certainty)
The first degree is referred to by the name 'ilm al-yaqîn (the
knowledge of Certainty), which means that Certainty is the result of
knowledge. At this degree the object of Certainty is knowledge just as
the aim of knowledge is Certainty. Both together are in the soul
uniquely, such that Certainty is the first degree of spiritual life
and the last of rough experience. This particular degree of mystical
yaqîn is the result of divine manifestation Act at the level of
existence and also the result of divine manifestation of lights of
nature at the dualistic level.

Ayn al-yaqîn (the Eye of Certainty)
The second degree of yaqîn is what one calls in Sufi terms ayn
al-yaqîn (the Eye of Certainty), that is, Certainty as a consequence
of meditation and vision. At this level, the object of Certainty is
present in front of the dualistic and is not only a tentative concept.
Here knowledge becomes what one calls 'ilm-e-huzuri'' (Presence of
knowledge), and that is the second aspect of Certainty in the
spiritual way and in liberating experience. By this kind of knowledge,
the man of the Way is distinguished from philosophers and learned men.
This particular degree of spiritual Certainty is the result of divine
manifestation of Attributes at the level of existence, just as it is a
result of manifestation of lights of the intellect at the level of
dualistic.

Haqq al-yaqîn (the total reality of Certainty)
Finally, the last degree of yaqîn is called haqq al-yaqîn (the total
reality of Certainty), that is, Certainty as supreme truth. Here,
Certainty has a particular coloring: it is the fruit of an
all-embracing experience because the object of Certainty is identical
to the one who is experiencing it, knowledge being transformed into
actual experience and actual experience into knowledge. At this stage,
in fact, knowledge is not limited to the intellect, nor to the vision
of the one who is contemplating it, it becomes one with the human
being. This is the final phase of yaqîn, the transcendent position of
the spiritual and intellectual journey. This high degree of Sufi
Certainty is the effect of the radiation of the divine manifestation
in Essence at its existential level and that of the diffusion of the
Light of lights (Dazzling Irradiations) at the level of the
manifestation of the dualistic.

Source: wikipedia