Arabic (Original)
وَبِهَذَا الْإِسْنَادِ عَنْ النَّبِيِّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ قَالَ إِذَا تَمَنَّى أَحَدُكُمْ فَلْيَنْظُرْ مَا الَّذِي يَتَمَنَّى فَإِنَّهُ لَا يَدْرِي مَا الَّذِي يُكْتَبُ لَهُ مِنْ أُمْنِيَّتِهِ.
English Translation
With the same chain, from the Prophet (peace be upon him) who said: "When one of you wishes for something, let him consider what he is wishing for, for he does not know what will be decreed for him from his wish."