وَعَلَى الْمَوْلُودِ لَهُ
“And upon the one to whom the child is attributed …” (Al-Baqarah 2:233, relevant wording)
The source says fi-hi isharah ila anna al-nasab ila al-abaʾ: the wording indicates paternal attribution. The relational particle in lahu is relevant to this implication.
The immediate context concerns financial duty. The source’s additional inference about lineage is isharah because it is textually indicated while not being the passage’s express purpose.