Is it obligatory to make up missed prayers after puberty for someone who started praying at the age of fifteen, or is repentance sufficient, and what is the lifetime make-up (al-qada' al-'umri) in light of the Qur'an and Sunnah?

Puberty is reached by nocturnal emission (wet dream), or the growth of coarse hair around the private parts, or by attaining the age of fifteen. For females, menstruation is an additional sign. Whichever of these signs appears first, the person is considered an adult (baligh) by it. If one reaches puberty by age and has maintained prayer, then there is no obligation to make up (qada') prayers. However, if one reaches puberty by nocturnal emission or hair growth, and then abandons prayer until the age of fifteen, the majority of scholars hold that they must make up those prayers. This is the more cautious approach and better for clearing one's conscience. The make-up prayers must be performed immediately, to the best of one's ability.