I do not know

"Hazrat Ibn Mas'ud said: 'He who gives opinion as soon as a question is put to him is mad.'...

Some wise man said: 'There are worshippers in the world. Their meal ends when they are still hungry. They sleep when it overcomes them. Their words end only in necessary talks.' In other words, they do not speak unless asked and they remain silent when sufficient reply is obtained from others...

Someone said that among the jurists, the greater number were men who used to say 'we don't know' than the numbers who used to say 'we know'..."

(Source: Imam Ghazzali's Ihya Ulum-id-Deen)

Whoa whoa whoa, slow down there
and do not commit yourself so soon.
For what will you answer on that Day
when asked
"From where did you get this?"

Verily, as the wise man said,
"I do not know" is half of learning,
and this is the shield of the learned man.

Such was the condition of the Companions (RA)
and those who preceded us in excellence,
who when asked,
would wish not except that someone else reply,
freeing them of their burden.

This is knowledge, and with its increase,
is the decrease of excessive talk.
As the wise learned (wo)men of the Hereafter knew.