There are three supplications that will undoubtedly be answered: the supplication of the oppressed, the supplication of the traveler, and the supplication of a parent against his child. [Ibn Maajah

«ثلاثُ دَعواتٍ مُستجابات لا شك فِيهن: دعوةُ المظلومِ، ودعوةُ المسافرِ، ودعوةُ الوالدِ على وَلدِه». [حسن.] - [رواه أبو داود والترمذي وابن ماجه وأحمد.]