It was narrated from Maimunah bint Sa`d, the freed slave woman of the Prophet (ﷺ) that :
the Messenger of Allah (ﷺ) was asked about illegitimate children. He said: "Two sandals in which I wage Jihad are better than freeing an illegitimate child." (ID)
English reference (ID): Vol. 3, Book 19, Hadith 2531 (ID)
Arabic reference (ID): Book 19, Hadith 2628 (ID)