He, sallallaahu ‘alayhi wa sallam, ordered her to perform night prayers:

Under category: How He treated them?

‘Ali ibn Abu Taalib narrated that the Prophet of Allah, sallallaahu ‘alayhi wa sallam, came to him and Faatimah one night, and he, sallallaahu ‘alayhi wa sallam, asked them: “Do you two not pray (at night)?” ‘Ali replied, “O Messenger of Allah, our souls are in the Hands of Allah, when he wishes to make us wake up, he will do so.” The Prophet of Allah, sallallaahu ‘alayhi wa sallam, left when I said that, and did not reply to me. Then I heard him when he was leaving, hitting his thigh and saying (what means): «But man has ever been, most of anything, [prone to] dispute.»

[Quran: 18:54]

Ibn Hajar said: “Ibn Battaal said: “This indicates the virtue of praying at night, and waking up one’s family if they are sleeping for that. If the Prophet of Allah, sallallaahu ‘alayhi wa sallam, had not known of the great reward of night prayers, he would not have bothered his daughter and cousin at a time of sleep. However, he chose that virtue for them over laziness, following the command of Allah (which means):

«And order your family with prayer.»”

[Quran: 20:132]

Ibn Battaal (a scholar) said: “His statement: ‘Then I heard him when he was leaving, hitting his thigh’ was because of the Prophet’s surprise at ‘Ali’s quick reply, and his disagreement with the excuse that he made. He did not like the excuse because he used predestination to leave off a responsibility, which is unacceptable. However, since the night prayers are only recommended and not obligatory, the Prophet of Allah, sallallaahu ‘alayhi wa sallam, simply left and said the verse, but if it had been an obligatory matter he would not have left without them performing it.”