Answered by Shaykh Sohail Hanif, SunniPath Academy Teacher
What do I do about the pre-fard sunnas if the fard (or khutba of Friday) starts?
Pre-fard sunnas if the fard (or khutba of Friday) starts
‘ Ala al-din ‘Abidinsays in al-Hadiyya al-‘Ala’iyya,
If one starts a [two rakat] supererogatory prayer.. or a make-up and the group prayer commences one doesn’t break ones prayer [but rather one completes the prayer and then joins the group]…One who begins the sunna prayer of Dhuhr or the Friday prayer and the group prayer commences [in the case of Dhuhr] or the Friday sermon commences, one concludes the prayer after praying two rakats so long as one hasn’t completed the third rakat with it’s prostration, in which case one completes four rakats, keeping the recitation short. [al-Hadiyya al-‘Ala’iyya, 107]
However, in the case that one cuts a four rakat sunna to two rakats, one would still be expected to pray the four sunnas after the fard prayer so as to offer the four rakats which are an emphasised sunna and are not replaced by any number of two rakat prayers.
‘Ala al-din ‘Abidinthen mentions,
Whoever finds the imam already offering the obligatory prayer with the group follows him and doesn’t busy himself with offering sunnas except in the morning prayer (salat al-fajr) if one is sure not to miss the prayer otherwise one leaves the sunnas and follows the imam. [ibid, 108]
Likewise if one were to enter the mosque and find that the Friday sermon has already commenced one just sits, and to pray a sunna prayer, including greeting the mosque (tahiyya al-masjid) would be prohibitively disliked. [ibid, 56].
And Allah knows best.