“No zakāh is due upon wealth until a full lunar year has passed over it.”

Narrated by Ibn Mājah (no. 1792), al-Dāraqutnī (no. 1889), and al-Bayhaqī in al-Sunan al-Kubrā (no. 7274), from the ḥadīth of ʿĀʾishah – may Allah be pleased with her.
Authenticated in Ṣaḥīḥ al-Jāmiʿ (no. 7497) and Irwāʾ al-Ghalīl (no. 787).

Brief Explanation of the Hadith

Zakāh is one of the pillars of Islām and among its great manifest symbols. It is incumbent upon every Muslim upon whom it is due to give it willingly and with a content heart, so that his wealth may thereby be purified and increased, and cleansed from impurities and defects.
In this ḥadīth, the Prophet — may Allah’s peace and blessings be upon him — clarifies some of the rulings pertaining to zakāh, namely that it does not become obligatory upon wealth until a full lunar year has passed over it.
What is meant by “wealth” (al-māl) here is the type of wealth that is subject to growth and increase, such as livestock, money, and trade goods.
And what is meant by “the passing of a year (al-ḥawl)” is that a complete lunar year passes while the wealth remains in the ownership of its possessor, on the condition that it has reached the niṣāb (the minimum threshold). The niṣāb of each category of wealth differs according to its type.
If the wealth does not reach the niṣāb, or if it reaches it but decreases below it during the course of the year, then zakāh is not obligatory upon it.
Thus, the attainment of the niṣāb and the passing of the ḥawl are two interdependent conditions for the obligation of zakāh.
The wisdom behind stipulating the passing of a year (ḥawl) is that growth and increase in wealth do not become apparent or ascertainable except after the lapse of a full year. This applies to wealth that is capable of growth, whereas in the case of non-growing wealth, such as crops and fruits, the ḥawl is not taken into account.
Rather, the consideration is given to the time of their ripening and harvest, at which point zakāh becomes due, as Allah the Exalted says:
“And give its due on the day of its harvest.” — Sūrat al-Anʿām (6:141)
Among the types of wealth for which neither the ḥawl nor the niṣāb is required are minerals (al-maʿdin) and buried treasure (al-rikāz); the zakāh on them is to be paid immediately upon extraction.