The Beloved Rasūl of Allâh Almighty şallAllāhu álayhi wa sallam stated,

It is wajib (obligatory) upon my Ummah to love Abū Bakr [rađiyAllāhu ánhu]

In another blessed Ĥadīth, the Beloved Prophet şallAllāhu álayhi wa sallam said,

It is wājib upon my Ummah to love Abū Bakr [rađiyAllāhu ánhu] and to be thankful to him

Reference:

Both Ĥadīths compiled in as-Sawaiq al-Muharriqa of Imām Ibn Ĥajar al-Haytamī rađiyAllāhu ánhu (d. 974h).