Is inviting to full hijab (with face and hand coverings) – as encouragement, not as an obligation – in this era considered a form of fanaticism, and is the female da'iyah (preacher) rewarded for it if it is sincerely for the sake of Allah, or must she remain silent due to her knowledge of the jurisprudential disagreement on the issue? Or is her appearance in full hijab sufficient for her to gain the reward of da'wah (invitation)?

Inviting women to observe the full hijab (definition) is not an exaggeration. Whoever knows the obligation for a woman to cover her face and hands in front of non-mahram (definition) men should advocate for it with wisdom and good counsel. The proofs for the obligation of covering the face and hands have been mentioned in previous fatwas. We recommend the books "The Return of the Hijab" and "Guarding Virtue" to increase adherence to and pride in the full hijab. Your adherence to this religious obligation is a silent invitation to others. If you are able to command the full hijab and advise with wisdom, then do not abandon that.