Assalam alaikum, I was reading the Mughni and found that if I lie I should repeat my wudu'. Nobody I know seems to have heard of this rule, not even my sheikh. Please tell me what I should do?

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.

Ibn Qudaamah did not mention in his book Al-Mughni that whoever lies his ablution is invalidated. It seems that you did not understood what he meant. He said: "Speeches that do not lead to apostasy such as lies, backbiting, obscene words and accusing someone of having committed Zina (fornication or adultery) do not invalidate ablution, and this is stated by Imaam Ahmad." The meaning of his statement means that ablution is not invalidated by forbidden talks like backbiting and telling lies except what leads to apostasy, if the talk is taking one out of the fold of Islam then it invalidates ablution, it is for this reason that he immediately mentioned after the above statement: "Ibn Al-Munthir said: "The scholars all over the Islamic world agreed in a consensus that accusing someone of Zina, false testimony, lies, backbiting do not require renewing ritual purity and do not invalidate ablution, but it is reported from many earlier scholars that they ordered a person to perform ablution after obscene talk and this is desirable in our view because of the scholars who ordered it, and we do not know any evidence about any talk which necessitates performing ablution. It is confirmed that the Prophet said: “If it happens for one to swear by Al-laata and Uzza, let him say La Ilaaha Illa Allaah (None has the right to be worshipped except Allaah)", and he did not order whoever said this to perform ablution.”

Therefore, it is not an obligation to perform ablution because of backbiting and telling lies, but this is something desirable according to some jurists out of taking a strict position against those who committed such sins to show them how serious those sins are. Indeed, some scholars are of the view that it is desirable to perform ablution after committing a sin, and this may be because performing ablution wipes out the sin as reported in an authentic narration. In fact Ibn Taymiyyah said: "It is desirable to perform ablution after having committed a sin."

Allaah Knows best.