You are going to meet people who received a Scripture, so let the first thing to which you invite them be to testify that there is none worthy of worship except Allah. [Al-Bukhari]
"إنك تأتي قوما من أهل الكتاب، فليكن أولَ ما تدعوهم إليه شهادة أن لا إله إلا الله" (البخاري)
