عِلْمًا عَلَّمَهُ وَنَشَرَهُ means knowledge a person taught and disseminated. The good produced by reliable knowledge can continue when later learners understand and use it properly. Merely spreading information without accuracy and care does not fulfill the same purpose.
Example 1: Teach a child to recite the Qur’an correctly.
Example 2: Teach a learner a beneficial skill with honesty.
Example 3: Prepare sound educational material useful to later students.
عَلَّمَهُ means “he taught it” and نَشَرَهُ “he spread it.” Both are past-tense verbs; the suffix ـهُ refers to the knowledge.