Ethics of the Fathers: Chapter 4 Mishnah 6 (1)
Rabbi Yishmael bar Rabbi Yose says: One who studies Torah in order to teach is given the means to study and to teach; and one who studies Torah in order to practice is given the means to study, to teach, to observe and to practice.
Avot 4:6
Ethics of the Fathers: Chapter 4 Mishnah 6 (2)
One who studies Torah in order to teach is given the means to study and to teach – If one intends to subsequently transmit material to others, he will inevitably delve more thoroughly and seek greater clarity of thought.
Rav Hirsch
Ethics of the Fathers: Chapter 4 Mishnah 6 (3)
One who studies Torah in order to practice is given the means to study, to teach, to observe and to practice – One who learns in order to act properly will be blessed with the ability to remember whatever information he needs in order to address the practical questions that arise.
Tiferet Yisrael