I'm telling you this for your own good; here's some friendly advice
A set phrase used when giving advice or a warning that the speaker believes is in the listener's best interest, often with a slightly paternalistic tone.
I'm telling you this for your own good: you'd better drop that matter.
Take my friendly advice: you should study more.
Variant using the kanji 事 for こと.
Variant with いわない in kana.
Variant with both 事 and kana いわない.
A fixed expression literally meaning 'I won't say bad things,' used idiomatically to preface well-meaning advice.