Abu Hurairah [may Allah be pleased with him] narrated that the Messenger of Allah (ﷺ) said:“No worshipper has ever said: None has the right to be worshipped but Allah (Lā ilāha illallāh)’ sincerely, except that the gates of heaven are opened for it, until it reaches to the Throne, so long as he avoids the major sins.”

English translation · Jami' at-Tirmidhi