Secret of Water

"And Devorah, a'h, was a prophetess... and she called Barak ben Avinoam, a'h, to go to war... And Barak said "If you go with me, I'll go, but if you will not come with me, I'll not go." We learn from this that Barak, zs'l, feared the enemy, mainly Sisra.

Midrash Aba Gurion, zs'l, explains who Sisra was, "There was not a man stronger than him. He was 30 years old when he captured that whole world with his mighty strength. There was not one large city that he did not destroy its walls with his mighty voice. Even the animals were afraid of him, when he raised his voice, the animals would not dare move. When he would go to war, 900 horses would carry him in his chariot, and when he returned, not one survived, he was so big and heavy, his weight sliced them like steel slices cotton. He would go to war with 40,ooo soldiers, 50,000 swordsmen, 60,000 spear fighters, 70,000 guards, 80,000 arrow shooters, and that's besides the additional 900 steel chariots with thousands of soldiers riding in it. Midrash Raba says that he also had 31 kings accompanying him. Sisra was the strongest man ever created. It says about him that when he would go to Nachal Kishon to drink water, the fish would get caught in his beard."

Sisra’s army was thoroughly defeated but Sisra escapes and hid in Yael's tent. He tells Yael to bring him water, but instead she gave him milk - מַיִם שָׁאַל חָלָב נָתָנָה

Sisera knew he was going to get killed and he purposely asked for water because he wanted to know...
מַיִם - מתי יבוא משיח - When will Moshiach come?

Yael gave him milk instead of water, thereby answering him:
חָלָב - חייבים לחזור בתשובה - We must repent!

Sisera ordered Yael to stand guard by the tent while he sleeps. A short while later, she saw he fell deep into sleep and she took a hammer and a big pin, the type which her tent was fastened to the ground. Carefully, she stood above him and drove the pin with the help of the hammer on his forehead. She banged the pin again and again deep into Sisra's forehead.

It was fitting that it should have been his brain that she dashed, since, as revealed by AriZal, Sisera's hold was in the brain and mind (DAAT).With the destruction of the unholy husk, the holy spark was released from the union of Sisera and Yael, and Rabbi Akiva, zs'l, descendant from this union.

A tremendeous hint that Rabbi Akiva, zs'l, descendant from Sisera is when Sisera asked Yael, "היש פה איש Is there a person here?". In Gematria value, יש פה is 395, same as Rabbi Akiva.

תורת ה' תמימה
HaShem’s Torah is a perfect whole.