And the second is indirect expression and allusion, which is akin to writing. An example is the poet’s saying:

Speech I delight in, such as listeners crave,
Carefully measured and weighed;
Her words strike true, yet sometimes she speaks in hints—
And the finest speech is that which hints.

The third is faulty grammatical inflection in speech. The essence of lahn is to turn speech away from its proper form, either into error or toward a hidden meaning for which the wording was not originally intended.

The point is that Allah, glorified is He, swore that the Prophet would recognize the hypocrites by the tenor of their speech.

Recognizing a speaker and what he conceals within himself through his words is easier than recognizing him through his outward marks and facial features. Speech indicates its speaker’s intention and inner thoughts more clearly than visible signs do. Discernment relates to both: observation and listening.

Al-Tirmidhī records a hadith narrated by Abū Sa‘īd al-Khudrī, may Allah be pleased with him, in which the Prophet, peace and blessings be upon him, said:

“Beware the believer’s discernment, for he sees by the light of Allah.”

He then recited the words of Allah Most High:

“Indeed, in that are signs for those with discernment.”