The Prophet’s restriction to those women is mercy *** from Him toward them, and thanks to the One of grace (Continuation of the answer to their second argument, in their claim that the Messenger is alive in his grave)

The Shaykh : And our Lord, Glorified and Exalted is He, has two forms of thanks for the servant. Allah, Mighty and Majestic, is greater in His thanks than we are: if a person draws near to Him by a span, He draws near to him by an arm’s length; if he draws near to Him by an arm’s length, He draws near to him by a cubit; and if he comes to Him walking, He comes to him running. And Allah, Glorified and Exalted is He, thanks the servant more than the servant thanks his Lord. For this reason, he (may Allah have mercy on him) said: “And our Lord has two forms of thanks for the servant”. And Allah the Exalted mentioned that al-Shakur (the Most Thankful) is among His names in several verses of the Qur'an.
“The Prophet’s restriction to those women is mercy *** from Him toward them”. “From Him” means from Allah. “Toward them” means toward the wives. It is a thanks for His blessings.
“And thanks to the One of grace” means that among the thanks of Allah, Mighty and Majestic, are mercy and thanks. And what is the meaning of “The Prophet’s restriction to those women”? It is that he does not marry anyone other than them and does not replace them with others.