The Prophet, peace and blessings be upon him, said:

“O Allah, purify my heart of my sins with water, snow, and hail.” 1

He also said in the funeral supplication:

“Wash him with water, snow, and hail, and cleanse him of his sins as a white garment is cleansed of dirt.” 2

Ṭahāra (purification)—and Allah knows best—means freedom from sins, for sins are impurity.
Zakāh combines the notion of this purification—the absence of sin—with the notion of growth through righteous deeds: forgiveness and mercy, deliverance from punishment and attainment of reward, the removal of evil and the acquisition of good.

A sudden, accidental glance is pardoned so long as one turns his eyes away, as is established in the Ṣaḥīḥ collections 3 from Jarīr, who said, “I asked the Messenger of Allah, peace and blessings be upon him, about the sudden glance, and he replied, ‘Turn your gaze away.’”

In the Sunan it is reported that he said to ʿAlī, may Allah be pleased with him:

“O ʿAlī, do not follow one glance with another; the first is for you, but the second is not.” 4

And in the Musnad and elsewhere it is related: “The gaze is a poisoned arrow from the arrows of Iblīs,” and in it: “Whoever looks at the beauty of a woman, then …”