Shaykh Bin Baz was asked:
Our Sister asks: Is the statement “Coincidence” and the statement “good luck” allowed or not?
“I do not know anything about this. If something happens coincidentally, that is, he meets brother of his for the sake of Allah without appointment in the street or with some brothers, then he says: I met you coincidentally, that is, without appointment, then there is no harm with this. Or he says: from good luck or from the facilitation of Allah I encountered so and so or I gave greetings to so and so or I made tawaf of the Ka’bah or I prayed Duha or I ordered good or prohibited evil…there is no harm in that. This is from his good luck/fortune as Allah, the Exalted said about the patience pious servants:
وَمَا يُلَقَّاهَا إِلَّا الَّذِينَ صَبَرُوا وَمَا يُلَقَّاهَا إِلَّا ذُو حَظٍّ عَظِيمٍ
none is granted it except the owner of the great portion [of the happiness in the Hereafter i.e. Paradise and in this world of a high moral character].
Whoever Allah provides steadfastness or Allah makes easy for him what He loves, then that is from his good luck/fortune which Allah made easy for him. If he meets a brother of his without appointment and he says: I met you by coincidence or I met so and so group by coincidence, then there is no harm in this because it is without appointment”
Faisal Ibn Abdul Qaadir Ibn Hassan