It is to give. The shukr (gratitude) of the elite among the elite (ahāss al-hawāṣṣ) is to recognize the blessings as coming from the One who bestows them. (Jāmiʿ, 61)
According to the people of verification, shukr is to acknowledge the blessing of the Bestower by humbling oneself before Him. In this broader sense, Allah the Exalted is described as al-Shakūr (the Most Grateful). The meaning here is that shukr, for the servants, is metaphorical. Just as the recompense for injustice is called injustice, and the recompense for evil is called evil, so too the recompense for shukr is called shukr.
It has been said that Allah's shukr is to grant abundant reward for little action. For example, when fat is taken from an animal in excess of the food it was given, that animal is called haywān shakūr.
It has also been said that the ḥaqīqa (inner reality) of shukr is to mention and praise the beneficence of the Giver. There is no difficulty in this. Thus, Allah the Exalted is called al-Shakūr because He praises His servants by mentioning their acts of obedience, which are in reality all forms of ihsan (spiritual excellence). The servant is called shakūr because he praises Allah by mentioning His blessings, which are the greatest forms of ihsan. (Jāmiʿ, 197)
Shukr is of two kinds: shukr with the tongue, which is well known; and shukr with the qalb (the heart), which is to devote oneself to self-observation while maintaining reverence (ḥurmah). It is also said that shukr is of three kinds: with the tongue, the qalb, and the body. (Jāmiʿ, 198)
Know that the roots of the maqāms (spiritual stations) attained by the branches of the ḥāl (spiritual states) of the people of yaqīn (certainty) are seven: tawba (repentance), sabr (patient endurance), shukr, rajāʾ (hope), khawf (fear), zuhd (asceticism), tawakkul (reliance upon God), maḥabba (love), and riḍā (contentment with God's decree). (Jāmiʿ, 218)
Someone has said: Shukr with the tongue is to acknowledge the blessing with humility. Shukr with the body is to act in accordance with Allah's commands and to serve Him. Shukr with the qalb is to devote oneself to self-observation while maintaining reverence.
Another has said: Shukr is to be so absorbed in witnessing the Bestower that one is absent from shukr itself.
Shiblī said: Shukr is not to see the blessing, but to see the Bestower.
Abū'l-Qāsim Junayd said: Shukr is not to use any of Allah's blessings in acts of disobedience.
Abū'l-Qāsim Sayqalī said: The ḥaqīqa of shukr is not to spend the blessing in masiyya (disobedience), and not to abandon obedience to Allah by hoarding wealth, knowing that the blessing comes only from the Bestower. He also said: The obligatory aspect of shukr regarding blessings is to praise and extol. The obligatory aspect of sabr regarding tribulations is to refrain from complaint. The ḥaqīqa of shukr is the removal of discontent. Only the truthful (ṣiddīq) can endure the bitterness of sabr, and only they can endure the sweetness of shukr.
I say: For this reason, some of the Companions (ṣaḥāba) said: 'We were tested with hardship and we were patient; we were tested with abundance and we could not be patient.'
He (Sayqalī) also said: Whoever does not realize that Allah's blessings come to him as a test, cannot understand the assaults of retribution that come with the succession of blessings. He also said: You have been made captives of tribulations so that you may become the pure ones among the blessed in the hereafter.
Abū ʿUthmān al-Maghribī said: The shukr of the common people is with food and clothing; the shukr of the elite is with the meanings that come to their qalb.
It has been said: According to the people of verification, the ḥaqīqa of shukr is to acknowledge the blessing of the Bestower by humbling oneself before Him.
It has been said: The ḥaqīqa of shukr is for the servant to see everything decreed for him as a blessing, except that which harms his religion.
It has been said: To acknowledge the blessings of the Bestower by praising Him.
I say: Shukr is something done with the qalb by acknowledgment, with the tongue by praise, and with the body by action. (Nabhānī, I, 313)