Mubahila is a non-Quranic term equivalent to a cursing contest where each contending party curses the other by uttering, "Allah's curse be upon you!" After conclusion, it is supposed to wreak havoc upon the liars.
3:61 If anyone argues with you concerning him (Jesus), after the knowledge has come to you, then say, “Come! Let us call upon our children, and your children, and our women and your women, and our people and your people to leave one another alone, knowing that God's condemnation is upon the liars.”
['Bahl' = To leave alone = Let someone hold on to his views = Let others do as they will. Interestingly, a term 'Mubahila' has been coined by Islamic clergy meaning 'a contest of mutual cursing'! This verse has been subjected to much conjecture through ‘Shan-e-Nuzool’, the circumstances of a revelation. Some exponents assert that the exalted Prophet is being told here to run a cursing contest with some Christians from Najran in Southern Arabia! Note that the word Mubahila does not appear in the Quran]