Silsilah as-Sahihah 3113 — Certainty of acceptance in supplication

It is narrated from Sayyiduna Abu Hurairah (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "Pray to Allah while you are certain of His response, and know that Allah does not accept the supplication from a heedless and inattentive heart."