ਸ਼ਸਤਰ ਹੀਨ ਕਬਹੂ ਨਹਿ ਹੋਈ, ਰਿਹਤਵੰਤ ਖਾਲਸਾ ਸੋਈ ॥Those who never depart their arms, they are the Khalsa with excellent
— Rehatnama Bhai Desa Singh
The kirpan/Siri Sahib is a dagger which symbolises a Sikh's duty to come to the defence of those in peril. All Sikhs should wear the kirpan on their body at all times as a defensive side-arm, just as a police officer is expected to wear a side-arm when on duty. Its use is only allowed in the act of self-defense and the protection of others. It stands for bravery and protecting the weak and innocent.
The kirpan is kept sharp and is actually used to defend others, such as those who are oppressed by harsh rulers, or a person who is being robbed, raped, or beaten. The true Sikh cannot turn a blind eye to such evils, thinking that they are "someone else's concern." It is the duty of the true Sikh to help those who suffer unjustly, by whatever means available, whether that means alerting the police, summoning help, or literally defending those who cannot defend themselves, even if that means putting oneself in harm's way.
Kirpan/Siri Sahib is one of 5 Sikh Kakars (Sikh essentials) of baptised/Amritdhari Sikh.