One Night with the Ohr Somei’ach

While Rav Ruderman was learning in Slabodka, a visitor came carrying a freshly printed Ohr Somei’ach. The young bochur wanted to borrow it, but the visitor said no, since he was leaving to continue his travels the following day.

Rav Ruderman was not discouraged. He asked for the sefer for a single night and promised to hand it back in the morning. By dawn he had worked through the whole sefer and mastered it.