Narrated by Thabit bin Ad-Dahhak (Radi-Allahu ‘anhu):
(who was one of the companions who gave the pledge of allegiance to the Prophet (Sallallahu ‘Alaihi Wa Sallam) underneath the tree (Al-Hudaibiya))
Allah’s Apostle (Sallallahu ‘Alaihi Wa Sallam) said, “Whoever swears by a religion other than Islam (i.e. if somebody swears by saying that he is a non-Muslim e.g., a Jew or a Christian, etc.), if his oath is false, he is really so. And a person is not bound to fulfill a vow about a thing which he does not possess.
And if somebody commits suicide with anything in this world, he will be tortured with that very thing on the Day of Resurrection;
And if somebody curses a believer, then his sin will be as if he murdered him; And whoever accuses a believer of Kufr (disbelief), then it is as if he killed him.”
Bukhari Vol. 8 : No. 73
…May Allah give us a better understanding & guide us to accept the truth