An individual wrote about his daily routine of reciting some verses of Holy Quran and passing on the reward (esal e thawab) to pious predecessors.
Hakim al Umma Mawlana Ashraf Ali Thanawi (Allah have mercy on him) appreciated the practice but made it clear that this must not be with the expectation that in return there will be spiritual benefit from their souls. This would be against sincerity. The passing on of rewards must be solely for Allah’s pleasure in appreciation of the services they provided in spreading the Deen.
Paraphrased from Tarbiyet us Salik,
Moreover, some people who do esal e thawab routinely are afraid that if they stop it, even for a genuine reason (poor health or lack of finances, etc.) there will wrath of these pious predecessors and some disaster will strike them. This is shirk. May Allah protect us all from this. Amin!