Practice what you preach

I am new at this sort of thing and any help I get would be appreciated. I am looking for the origins of the expression 'Practice what you preach'. I came across it in an Arabic piece entitled "O Son" but have no idea if this is first use. Any thoughts?

Is it biblical? Others will pretty certainly know.

People have been expressing this sentiment in English since at least the 14th century. E.g. this from Piers Plowman -

"He performeth evil: that he preacheth, he proveth [i.e. shows] not".
Or from The Merchant of Venice -
"It is a good divine that follows his own instructions".
And in a translation of Seneca published by R L'Estrange in 1678 the proverb appears in its modern form -
"We must practise what we preach".