"These are the precepts that have no prescribed measure: the corner of a field [which must be left for the poor], the first fruit offering, the pilgrimage [to the Temple Mount], acts of kindness, and Torah study."
Mishna, Peah 1:1

"These are the precepts whose fruits a person enjoys in This World but whose principal remains intact for him in the World to Come. They are: the honor due to father and mother, acts of kindness, early attendance at the house of study morning and evening, hospitality to guests, visiting the sick, providing for a bride, escorting the dead, absorption in prayer, bringing peace between man and his fellow, and the study of Torah is equivalent to them all."
Talmud, Shabbat 127a