Sayyiduna Ibn Umar and Sayyidah Aishah (may Allah be pleased with them) said that the Messenger of Allah (peace and blessings be upon him) said: "Whoever seeks a right, let him seek it with decency, whether it is paid in full or not."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب البيوع / 10980