استح من ذم من لو كان حاضرا لبالغت في مدحه, و مدح من لو كان غائبا لسارعت الى ذمه
It's a proverb that means "Don't speak about people behind their backs" i.e. the proverb is especially intended for hypocrites.
I tried to correct it so that it would make more sense.
Its literal translation will be separately as follows:
1- استح من ذم من لو كان حاضرا لبالغت في مدحه
Don't dispraise him, whom you would have praised in presence.
2- و مدح من لو كان غائبا لسارعت الى ذمه
And don't praise him, whom you would have dispraised in absence.
I wish it could help...