Upon whom is it obligatory to call to Allah?

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Check below answers in case you are looking for other related questions:
How should he call his friend to the way of al-Sunnah wa’l-Jamaa’ah?
Are the Sufi shaykhs really in contact with Allaah?

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How should he call his friend to the way of al-Sunnah wa’l-Jamaa’ah?
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