Benedict recalled "with gratitude Cardinal Sins unfailing commitment to the spread of the Gospel and to the promotion of the dignity, common good and national unity of the Philippine people," he said in the telegram, written in English, to Rosales and released by the Vatican.
"I join with you in praying that God, our merciful father, will grant him the reward of his labors and welcome his noble soul into the joy and peace of his eternal kingdom."
Cardinal Sin, a hugely influential Roman Catholic spiritual leader who helped to topple two Philippine presidents, died in hospital Tuesday of multiple organ failure after a lengthy struggle with kidney problems and diabetes. He was 76.
Poor health prevented him from taking part in the conclave that chose German Cardinal Joseph Ratzinger to succeed the late Pope John Paul II.
Sin and Ratzinger, who became Pope Benedict, knew each other well since being named cardinals by Pope John VI, in 1976 and 1977 respectively.
Sins private secretary Father Rufino Sescon said the cardinal had been deeply affected by the death in April of his friend Pope John Paul II, possibly leading to a deterioration in his own condition. AFP, AP