Tafsir of Qaf 50:37

{For whoever has a heart} Meaning: A receptive heart. For he whose heart does not comprehend is as if he has no heart at all.

{And lends an ear} Meaning: Listening attentively.

{While he is present} Meaning: Present with his intellect. For he whose mind is not present is as if he were absent. Imam Abd al-Qahir wittily remarked to one of his students: Whatever you wish of flowery speech, while the youth Is in Misqlabad, for the watering of crops.

Or it means: He is a believer, witnessing to its truth and that it is revelation from God. Or: He is one of the witnesses mentioned in His saying: {That you may be witnesses over the people} (Al-Baqarah: 143).

Qatadah said: He is a witness to its truthfulness from among the People of the Scripture, due to the presence of its description with him.

Al-Suddi and a group read it as ulqiya al-sam'u (passive voice). Its meaning: For one to whom another has lent an ear and opened his hearing, but he has not brought his mind, while he [the subject] is present-minded and perceptive. It is also said: He lent his hearing, or hearing was lent from him.

{And We certainly created the heavens and the earth and what is between them in six days, and no weariness touched Us. So be patient, [O Muhammad], over what they say and exalt [Allah] with praise of your Lord before the rising of the sun and before the setting. And [part] of the night exalt Him and after prostration. And listen for the Day when the Caller will call out from a near place. The Day they will hear the blast in truth; that is the Day of Emergence. Indeed, it is We who give life and cause death, and to Us is the destination.}