"[Take] from their wealth," meaning: accept, "a charity that purifies them" from their sins, "and causes them to grow by it." This is not the obligatory charity, but rather it is an expiation for them. "And pray for them," meaning: seek forgiveness for them, "for your prayer is a source of peace for them," meaning: a tranquility for their hearts. Allah—Mighty and Majestic—says this to the Prophet (peace and blessings of Allah be upon him).