Translation:Shulchan Aruch/Orach Chaim/238
238: To Set Aside Times for Torah at Night.
1 A person needs to be more careful about learning at night than during the day, and one who abstains from it – his punishment is great.
2 If he has a set schedule to learn a specific amount during the day, and he was busy during the day and did not fulfil it, he should fulfil it immediately at night.