Mu'jam al-Saghir

Explanation:
1:
That is, the original place for tying the lower garment (tahband) is up to the middle of the shin; if one wishes to wear it lower than that, then there is allowance to keep it up to just above the ankles. To wear it lower than this is prohibited.

Benefits and Issues:
➊ The lower part of the calf muscle is located between the knee and the ankle; this is why, in the following hadith, the word "half of the calves" is mentioned.

➋ The original ruling is that the lower garment, pajama, Arabic shirt, etc., should be kept up to the middle of the calves; keeping it lower than this is permissible but not preferable.

➌ A man's garment should remain above the ankles.

English Translation:

It is necessary to cover the knees with the izar (lower garment). Under no circumstances—whether in bowing (ruku‘), prostration (sujud), work, etc.—should the knees be visible, and the ankles must remain uncovered at all times. It is not correct to wear it above the middle of the shin, nor below the ankles. Based on custom and tradition, one may wear it anywhere in between as deemed appropriate. The shalwar (trousers) also falls under the same ruling as the izar; therefore, it too should be kept above the ankles. True beauty lies only in obedience to Allah and His Messenger (sallallahu alayhi wa sallam).

Benefit:
In any situation, wearing clothes (such as shalwar, pajama, pants, qamees, shirt, turban, or handkerchief, etc.) below the ankles is a major sin. Whether in happiness or sorrow, in the mosque or on the playground, at school or at any function, at every occasion it is obligatory to keep the ankles uncovered. A woman, in every situation, must keep her ankles covered.