Reb Elazar Tzaddok Turchin zt'l was a masmid already as a young bachur, but the following incident elevated his knowledge and hasmadah to a very high level.
Erev Yom Kippur, after the seudah hamafsekes, he was going towards the beis medresh to say Tefillah Zakkah in preparation for Yom Kippur. But when he passed the Tepliker Rav's zt'l home, the rav called to him, "Bachur'l! Bachur'l! I need some help cleaning my home."
Reb Elazar Tzaddok put aside his aspirations to be in beis medresh early and helped the elderly Tepliker Rav. When he completed this good deed, the Tepliker Rav told him, "I know it is late, and you have many things to do. You helped me with mesirus nefesh. In return, I'm certain that Hashem will help you this year beyond the laws of nature."
Indeed, after this incident, Reb Elazar Tzaddok Turchin became a new person. He was able to learn thirty pages of Gemara a day, and he didn't forget anything.
Reb Meir Chadash zt'l, the mashgiach of Yeshivas Chevron, saw how his student, Reb Elazar Tzaddok, was finishing one masechta after the other and suspected that he was learning on a superficial level. So he tested him, and Reb Elazar Tzaddok knew everything perfectly.
Reb Meir Chadash didn't know the secret, the reason Reb Elazar Tzaddok Turchin's mind was so open for Torah, beyond the rules of nature.
Reb Elazar Tzaddok continued studying in this manner, and he became a great Torah scholar. (Years later, he wrote the sefarim Shoneh Halachos together with Reb Chaim Kanievsky shlita.)
Reb Elazar Tzaddok helped the Tepliker Rav on erev Yom Kippur, but ultimately, he did himself the greatest favor. He earned dividends from this chesed for the rest of his life.
Because for doing chesed one earns reward also in this world.
Rebbe Henoch of Alexander zt'l said chesed is mesugal for bearing children. He explained that שערי הולדה, the chambers in heaven for bearing children are sometimes closed. But right near this chamber is שערי גמילות חסדים, the chamber of loving-kindness. So, even if the gates to the chambers for children are closed, one can enter through the gates of gemilus chasadim, and from there it is easy to jump into the chambers for children.
Rebbe Baruch of Zichlin zt'l came to Rebbe Henoch of Alexander zt'l for Shabbos Parashas Noach, and he told the Rebbe that his son-in-law doesn't yet have any children.
Rebbe Henoch told him to do chesed, because the chamber for children is near the chambers for chesed. He added that this is alluded to in Rashi (6:9), עיקר תולדותיהן של צדיקים מעשים טובים. This can be translated, עיקר תולדותיהן של צדיקים, tzaddikim have children, מעשים טובים, in the merit of their gemilus chasadim. Therefore, the next pasuk states, ויולד נח שלשה בנים את שם ואת חם ואת יפת, "Noach gave birth to three children: Shem, Cham, and Yafes." Noach bore those children because he was involved in doing chesed.
In particular, tzedakah and giving interest-free loans are mesugal for bearing children and for having good children. The Gemara (Bava Basra 9:) states, "Whoever gives tzedakah regularly, Heaven will grant him children who are wise, wealthy, and learned in all aspects of the Torah."
And it states (Tehillim 37:26) כל היום חונן ומלוה וזרעו לברכה, "All day long he is compassionate and he lends money and his children will be blessed." This hints that by giving tzedakah and loans, one merits having good children. (The Divrei Avraham said this explanation to the Chasam Sofer zt'l, and the Chasam Sofer zt'l praised it.)