That the Messenger of Allah (ﷺ) said: "Three will not be spoken to by Allah on the Day of Judgement, nor will they be purified, and for them is a painful torment: A man that gave a pledge to an Imam, and if he gives to him he fulfills it, and if he does not give to him he does not fulfill not fulfill it." [Abu 'Eisa said:] This Hadith is Hasan Sahih.
حَدَّثَنَا أَبُو عَمَّارٍ، حَدَّثَنَا وَكِيعٌ، عَنِ الأَعْمَشِ، عَنْ أَبِي صَالِحٍ، عَنْ أَبِي هُرَيْرَةَ، قَالَ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم ثَلاَثَةٌ لاَ يُكَلِّمُهُمُ اللَّهُ يَوْمَ الْقِيَامَةِ وَلاَ يُزَكِّيهِمْ وَلَهُمْ عَذَابٌ أَلِيمٌ رَجُلٌ بَايَعَ إِمَامًا فَإِنْ أَعْطَاهُ وَفَى لَهُ وَإِنْ لَمْ يُعْطِهِ لَمْ يَفِ لَهُ . قَالَ أَبُو عِيسَى هَذَا حَدِيثٌ حَسَنٌ صَحِيحٌ وَعَلَى ذَلِكَ الْأَمْرُ بِلَا اخْتِلَافٍ.
Tirmizi
The Book on Military Expeditions • Hadith 1639