Final answer:
The phrase from the Emancipation Proclamation relates to the creation of the 13th, 14th, and 15th Amendments, which protected the rights and freedoms of newly freed slaves.
Step-by-step explanation:
The phrase 'the people whereof shall then be in rebellion against the United States, shall be then, thenceforward, and forever free' from the Emancipation Proclamation is related to the creation of the 13th, 14th, and 15th Amendments of the United States Constitution, also known as the Reconstruction Amendments.
These amendments were intended to protect the rights and freedoms of the newly freed slaves following the Civil War. The 13th Amendment permanently abolished slavery, the 14th Amendment granted citizenship and equal protection to African Americans, and the 15th Amendment gave Black men the right to vote.