Whenever you recite Kalimah Tayyabah, then make intention that the reward should be bestowed upon to you then and also at the time of dying and then pray Allah Almighty to keep its blessing on your future generations and also bless them with its reward till their last breath. Reciting this Kalimah for once would result in 4000 blessings and if granted to a deceased will have 4000 virtues to enter into their grave.