When the Messenger of Allah was sent to the polytheists to call to this statement, 'None has the right to be worshipped save Allah,' they understood from it that made them reject it, oppose the messenger, and all those who believed in it. What was this understanding? Was it the understanding that Allah existed and was One? They already believed in this. They believed that He was The Creator, The Nourisher, The Sustainer, in His hands was the control of all affairs, and in His hands was life and death. It was said to al-Hasan, 'People say that whoever says, 'None has the right to be worshipped,' shall enter Paradise.' He said, 'Whoever says, 'None has the right to be worshipped,' and fulfills its obligations and meets its requirements shall enter Paradise.' Wahb ibn Munabbih was asked, 'Is not the testification that 'none has the right to be worshipped save Allah' the key to Paradise?' He replied, 'Of course, but every key has its teeth: if you bring a key that has teeth, the door shall open; but if not, it will not.' My Brothers! Strive, today, to your utmost in actualising Tawhid, for nothing else can take you to Allah. Be desirous for establishing its rights for nothing else will save you from the punishment of Allah. The testification of Tawhid has many great benefits, it is not possible to enumerate them all, however, the author mentions fifty-five benefits of it. This small treatise deals with the correct and accurate meaning of the testification of Tawhid and with an extremely beneficial appendix - They Types of Hearts - by al- Hafiz ibn Qayyim al-Jawziyyah