The 'ignorant ulamas (Islamic scholars)' are those who seek the knowledge to gain respect among the people and to use it in enjoyment of the worldly benefits.
The details of the ignorant scholars are found in the hadith of the Prophet (may Allah bless him and grant him peace).
Narrated Abu Hurayrah:
The Prophet (may Allah bless him and grant him peace) said: If anyone acquires knowledge that should be sought seeking the Face of Allah, but he acquires it only to get some worldly advantage, he will not experience the arf, i.e. the fragrance, of Paradise.
Therefore, it is necessary to be vigilant in the demand for religious knowledge, to purify one's intentions, and to act solely on the pleasure of Allah.
Narrated Ibn Umar:
The Prophet (may Allah bless him and grant him peace) said: "Whoever learns knowledge for other than (the sake of) Allah, or intends by it other than Allah, then let him take his seat in the Fire."
In this hadith the Prophet (may Allah bless him and grant him peace) emphasizes the need for knowledge only for Allah, for the sake of Allah. He says that if anyone's intention is broken, that is, he will go to hell if he learns knowledge for a purpose other than Allah and for the sake of other than Allah.
Narrated Ibn Ka'b bin Malik:
The Messenger of Allah (may Allah bless him and grant him peace) saying: "Whoever seeks knowledge to contend with the scholars, or to use it to argue with the fools, and to have people's faces turn towards him, then he shall be admitted to the Fire."