The reward for Sileh Rahmi has been described by the Holy Prophet (s.a.w.s.) in one of his traditions. He says:
"When a person goes towards his relatives so that he can fulfill his rights with his life and his wealth, Allah bestows upon him the reward of a martyr at every step he takes. He (Allah) writes down forty thousand Hasana (the unit of Divine rewards) and He erases forty thousand of his sins and He elevates him by forty thousand grades. The person achieves the position of one who has worshipped Allah for a hundred years."
(Behaarul Anwaar)
At another place the Holy Prophet (s.a.w.s.) says, regarding the rewards for Sileh Rahmi:
"The reward for Sadaqah in the way of Allah is ten times, whereas the reward for giving a loan is twelve times (because in giving a loan the dignity of the Loanee is maintained). The reward for the good behaviour to the believing brothers is twelve times and the reward for Sileh Rahmi is twenty four times."
(Behaarul Anwaar)
source : GREATER SINS by Ayatullah-ul-Uzma Sayed Abdul Husain Dastghaib Shirazi (r.a.)