There's a hadith as follows:
Al-Bukhaari reported that the Prophet (peace and blessings of Allaah be upon him) said: "Whatever of the izaar (lower garment) is below the ankles is in the Fire." (al-Bukhaari, no. 5787)
I have seen lots of people wear socks, which are of course below ankles, and pray namaz. Does that mean they will be in hell fire?