Sayyiduna Abu Huraira (may Allah be pleased with him) narrates that the Messenger of Allah (peace and blessings be upon him) said... and he narrated this hadith: "When any one of you desires something, he should see what he is desiring, because he does not know what may be written for him from his desire."
Hadith Referenceمسند الشهاب / 768
Hadith Gradingمحدثین:إسناده حسن
Hadith Takhrij«إسناده حسن ، وأخرجه أحمد : 357/2، الادب المفرد : 794، طيالسي : 2462»
Brief Explanation
Explanation: The meaning is that desires and wishes should be made thoughtfully and with understanding, because a person does not know whether what he is asking for is beneficial or harmful for him. A person does not know which desire is useful for him and which is harmful. If he makes a wrong wish, it is possible that he may get exactly that, and thus his own desire and wish may become the cause of his harm. Therefore, a person should always wish for good things and seek Allah Ta'ala’s mercy and goodness.