Buddha's sermons can be found in the Sutta Pitaka.

Sutta Pitaka is one of the three sections of the Tripitaka, the sacred scriptures of Buddhism. It is also known as the "Basket of Discourses" and contains the Buddha's teachings in the form of sermons, dialogues, and speeches. The Sutta Pitaka is considered the most important section of the Tripitaka as it contains the actual words of the Buddha.

The Sutta Pitaka is further divided into five collections, known as Nikayas. These Nikayas are:

1. Digha Nikaya (Collection of Long Discourses): This collection consists of 34 suttas or discourses, which are longer and more elaborate in nature. These discourses cover a wide range of topics, including ethics, meditation, and philosophical teachings.

2. Majjhima Nikaya (Collection of Middle-length Discourses): This collection contains 152 suttas, which are of medium length. The discourses in this collection focus on various aspects of Buddhist teachings, including the Four Noble Truths, the Eightfold Path, and the practice of mindfulness.

3. Samyutta Nikaya (Collection of Grouped Discourses): This collection consists of 2,889 suttas grouped together based on their thematic content. The discourses in this collection cover a wide range of topics, including the aggregates of existence, dependent origination, and the nature of consciousness.

4. Anguttara Nikaya (Collection of Numerical Discourses): This collection contains suttas arranged in numerical order, starting from ones and progressing up to elevens. The discourses in this collection cover various topics, including the gradual training, the virtues to be cultivated, and the factors of enlightenment.

5. Khuddaka Nikaya (Collection of Minor Discourses): This collection is a compilation of miscellaneous texts, including verses, hymns, and short discourses. It includes popular texts such as the Dhammapada, the Udana, and the Itivuttaka.

Overall, the Sutta Pitaka contains a vast collection of Buddha's teachings, covering a wide range of topics related to ethics, meditation, philosophy, and practical guidance for leading a virtuous life. It is considered an essential scripture for Buddhist practitioners and scholars alike.