It is the statement of Islām and the key to the Abode of Peace (Paradise)
Ibn al-Qayyim (d. 751AH), may Allāh have mercy upon him, said:1
I bear witness that there is no deity worthy of worship except Allāh Alone; the One Who has no partner. A declaration by which the heavens and the earth were established, the entire creation was created, and with which Allāh, the Most High, sent His Messengers, revealed His Books, and prescribed Islamic laws. Because of it, the scales were appointed, the records established and the marketplace for Paradise and Hell-Fire was erected. On account of this declaration, creation was divided into the believers and the disbelievers, the pious and the wicked. It is the purpose for creation, commandment, reward and punishment. It is the sole truth for which the creation was fashioned. The questioning and reckoning (of man) will be about this testification and its associated rights; and it is upon this testification that reward and punishment will be doled out.
Upon it, the Qiblah was assigned, the religion was founded, and the swords of Jihād were unsheathed. It is Allāh’s sole right upon all the servants. It is the statement of Islām and the key to the Abode of Peace (Paradise). It is the reason for which both the prior and later generations will be questioned. For surely, the feet of the slave will cease to move from before Allāh until he is questioned concerning two matters: “Who did you worship?” and “How did you respond to the Messengers?”
So the response to the first question is through fulfilling: “There is no deity worthy of worship save Allāh Alone,” in knowledge, affirmation, and action.
And the response to the second question is through fulfilling “Muḥammad, may Allāh raise his rank and grant him peace, is the Messenger of Allāh,” in knowledge, affirmation, submission, and obedience.2 He was sent with the true religion and the straight path. Allāh sent him forth as a mercy to al-ʿĀlamīn,3 as a leader for the righteous, and as a proof against the whole of creation.
He sent him following a cessation of the Messengers, and thereby guided, through him, to the most upright of ways and the clearest of paths. He (Allāh) obligated the servants to obey, assist, honor, and love him, may Allāh raise his rank and grant him peace, and to fulfill his rights.
He barred all paths to His Paradise, so they shall not open for anyone save through the [Messenger’s] path. He opened his breast, elevated his mention, and removed from him his burden. He rendered humiliation and misery upon those who defy the Prophet’s commands.
In the Musnad (of Imām Aḥmad), there occurs a ḥadīth of Abī Muneeb al-Jurashee from ʿAbdillāh b. ʿUmar, who said:
The Messenger of Allāh, may Allāh raise his rank and grant him peace, stated:
I was sent with the word just before the Last Hour, so that Allāh is worshiped alone without partners. My sustenance was provided for me under the shadow of my spear. Those who oppose my command were humiliated and made inferior, and whoever imitates a people, he is one of them.
Just as humiliation covers those who oppose his command, might is for the people who obey and follow him.