It is narrated from Sayyiduna Abdullah bin Amr (may Allah be pleased with them both) that the Prophet (peace and blessings be upon him) said: "Repaying a favour in kind is not joining the ties of kinship; rather, the one who truly joins the ties of kinship is he who, when the relationship with him is cut off, joins it, that is, he restores the tie by upholding kinship."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب قسم الصدقات / 13219