Muhammad said: He means the mixing of the man's fluid with the woman's fluid. It is said: "I mingled it (mashajtu-hu)," and thus it is "mingled (mashij)." "We test him (nabtalihi)" means: We put him to the test.
قَالَ محمدٌ: يُرِيدَ اخْتِلاطَ مَاءِ الرَّجُلِ بِمَاءِ الْمَرْأَةِ، يُقَالُ مَشَجْتُهُ فَهُوَ مشيج. ﴿نبتليه﴾ نختبره.