“The best companion is Fatima’s Mahdi”
The translation of verse 69 of Surah An-Nisa:
And whoever obeys Allah and the Messenger - those will be with the ones upon whom Allah has bestowed favor of the prophets, the steadfast affirmers of truth, the martyrs and the righteous. And excellent are those as companions.
Zurara has narrated from Imam Baqir about the interpretation of this verse: “In this verse “messenger” refers to Muhammad- the Messenger of Allah, “affirmers of truth” refers to Ali ibn Abi Talib, “martyrs” refers to Hassan and Hussein, “righteous” refers to the infallible Imams, and the “excellent companion” is Imam Mahdi.
Al-dhaam al Naseb, v. 1, p. 57