Valmiki Ramayana Kishkindha Kanda Sarga 30 Shloka 71

उपपन्नानाम् approached, पूर्वम् earlier, उपकारिणां च and who has helped, अर्थिनाम् the one who requested , संश्रुत्य with regard to, आशाम् hopes, यः he who, हन्ति disappoints, सः he, लोके on the earth, पुरुषाधम: lowest among men.

'He who, having promised to his friend to grant his desire and who, having been obliged, fails to implement the promise, is the lowest on earth.