The Kalimahs came into existence to facilitate the easy memorising and learning of Aqeedah (beliefs). It has no Shar’ee compulsion as far as its memorising is concerned. When they came into existence is not known.
A true Muslim is someone who is completely aware of the meaning of the Kalima, proclaims it with sincerity and devotion, and acts and lives in accordance to its requirements. This is why a Muslim should read there 6 kalimahs daily and act upon what they say.....
1. Kalima-e-Tayyabah (Word of Purity)
There is none worthy of worship except Allah and Muhammad is the Messenger of Allah.
Kalima-e-Shahaadat (Word of Testimony)
I bear witness that none is worthy of worship but Allah, the One alone, without partner, and I bear witness that Muhammad is His servant and Messenger.
Kalima-e-Tamjeed (Word of Glorification)
Glory be to Allah and praise to Allah and there is none worthy of worship but Allah, and Allah is the Greatest. And there is no might or power except with Allah, the Exalted, the Great One.
Kalima-e-Tauhid (Word of Unification)
There is none worthy of worship except Allah. He is alone and has no partner. To Him belongs the Kingdom and for Him is all praise. He gives life and causes death. In His hand is all good and He has power over everything.
Kalima-e-Astaghfar (Word of Penitence)
I seek forgiveness from Allah, who is my Creator and Cheriser, from every sin I committed knowingly or unknowingly, secretly or openly. I also seek His forgiveness for all sins which I am aware of or am not aware of. Certainly You (O Allah!), are the Knower of the hidden and the Concealer of mistakes and the Forgiver of sins. And there is no power and no strength except with Allah, the Most High, the Most Great.
Kalima-e-Rud-e-Kuffr (Word of Rejection of Disbelief)
O Allah! Certainly I seek protection with You from, that I associate partner with You anything and I know it. And I seek forgiveness from You for that I do not know it. I repended from it and I made myself free from disbelief and polytheism and the falsehood and the back-biting and the innovation and the tell-tales and the bad deeds and the blame and the disobedience, all of them. And I submit and I say (there is) none worthy of worship except Allah, Muhammad is the Messenger of Allah.
Jazaak'allah Khair for reading.