The confirmation that Muhammad has the prophetic seal is found in the Qur'an.
PICKTHAL : Muhammad is not the father of any man among you, but he is the messenger of Allah and the Seal of the Prophets; and Allah is ever Aware of all things. Surah 33:040
What does the word "seal" indicate? To the Muslim it as a double meaning, first it means that Muhammad is the "last prophet, or the "final prophet" These terms denote "finality", there is no other prophet to come after Muhammad, which serves to prove the supremacy of Muhammad's calling as a prophet of Allah.
The second meaning is that Muhammad displayed a physical abnormity on his back, between his shoulder blades, The historical accounts differ as to the size and shape, some called it a birth mark, while other described it as a mole shaped like a small button found on a tent, while others described its shape as a small egg.
Narrated As-Sa'ib bin Yazid:
My aunt took me to the Prophet and said, "O Allah's Apostle! This son of my sister has got a disease in his legs." So he passed his hands on my head and prayed for Allah's blessings for me; then he performed ablution and I drank from the remaining water. I stood behind him and saw the seal of Prophethood between his shoulders, and it was like the "Zir-al-Hijla" (means the button of a small tent, but some said 'egg) . Sahih Bukhari 1:189
Muslims claim the physical "seal" denotes the fulfillment of the prophecy found in the Bible, the seal repersents the "government".
For unto us a Child is born, Unto us a Son is given; And the government will be upon His shoulder. And His name will be called Wonderful, Counselor, Mighty God, Everlasting Father, Prince of Peace. Isaiah 9:6
Islamic Scholars also claim that the Biblical passage, John 6:27b, is the prophetic fulfillment of the prophet Muhammad due to fact that Jesus refers to a "seal".
because God the Father has set His seal on Him." John 6:27b.
Here is the verse in proper context:
Jesus answered them and said, "Most assuredly, I say to you, you seek Me, not because you saw the signs, but because you ate of the loaves and were filled. Do not labor for the food which perishes, but for the food which endures to everlasting life, which the Son of Man will give you, because God the Father has set His seal on Him." John 6:26-27
When the verse is shown in its proper context it is speaking of the "Son of Man", Jesus as having the seal. Muslims do not refer to Allah as "Father".
Muhammad: Model to Mankind
YUSUFALI: Ye have indeed in the Messenger of Allah a beautiful pattern (of conduct) for any one whose hope is in Allah and the Final Day, and who engages much in the Praise of Allah. Surah 033.021
YUSUFALI: Nun. By the Pen and the (Record) which (men) write,
Thou art not, by the Grace of thy Lord, mad or possessed.
Nay, verily for thee is a Reward unfailing:
And thou (standest) on an exalted standard of character.
Surah 068.001-004