Jews, where in Torah has it been mentioned about...?

It's not in the Torah, it's in the Talmud.

According to the Talmud (tractate Taanit 2a), prayer is a Biblical command: "'You shall serve God with your whole heart.' (Deuteronomy 11:13) What service is performed with the heart? This is prayer." The prayers are therefore referred to as Avodah sheba-Lev ("service that is in the heart").

The Talmud also (in tractate Berachoth 26b) gives two reasons why there are three basic prayers:

Each service was instituted parallel to a sacrificial act in the Temple in Jerusalem: the morning Tamid offering, the afternoon Tamid, and the overnight burning of this last offering.

According to Rabbi Jose b. Hanina, each of the Patriarchs instituted one prayer: Abraham the morning, Isaac the afternoon and Jacob the evening prayers. This view is supported with Biblical quotes indicating that the Patriarchs prayed at the times mentioned. However, even according to this view, the exact times of when the services are held, and moreover the entire concept of a mussaf service, are still based on the sacrifices.

The term "fasting" is usually how "afflict" yourself is translated. So, where Torah says to "afflict yourself" most Jews see "fasting" etc.

A great many of the interpretations on what Torah is saying is in the Talmud, not the Bibles themselves. As for prayers, the traditions for 3 prayers a day often is a conservative attempt to meet what the Torah shows as best examples. So, someone did a study and saw Moses may have prayed three times in one day and...we got a ritual.

I can no longer resist the pizza. I open the box and unzip my pants with my other hand. As I penetrate the gooey cheese, I moan in ecstasy. The mushrooms and Italian sausage are rough, but the sauce is deliciously soothing. I blow my load in seconds. As you leave the bathroom, I exit through the front door....