Book: Tafsir of Ayashi (urdu translation)
Translation contributed by brother Jhangvi
Prophet [sallalahu alaihi wa ala alihi wa sallam] asked Usama [R.A]: Why did you killed him, when he was reading (about to read) the Kalimah? Usama [R.A] replied: He was reciting the Kalimah just to escape (to save his skin). Thereupon Prophet [sallalahu alaihi wa ala alihi wa sallam] said: Had you torn his heart to see whether he was reciting the Kalimah from his heart or not? Then He [sallalahu alaihi wa ala alihi wa sallam] ordered to deliver all his wealth and goats to his family [Tafsir Hasnaat, 1/818]. Thereafter Usama [R.A] made a promise (to himself) that in future, I will not kill anyone such, who would be reciting the Kalimah. He also said Salam after adhering to Islam. When the battles came upon Ali [R.A] (during his Caliphate), then Usama [R.A] mentioned about his promise and excused himself (from the battles). Sheikh Faiz says: this narration tells us about the Nifaaq (hypocrisy) of Usama [R.A],for that is why he remained away from Ali [R.A] (in his battles), and such excuse of Usama [R.A] is not acceptable….
Didnt al majlisi also wrote that usama ibn zayd was appointed to lead the hypocrites? I remember reading it in hayat al qulub & i think its in chapter about prophet’s last days.