A husband's response to his wife's vow reveals a moment of deep marital agreement and shared spiritual vision. Although Hannah made the commitment independently, and Elkanah possessed the legal authority to cancel her vow on the day he heard it, he instead chooses to embrace it completely [מלבי״ם]. He fully supports her practical plans, encouraging her to remain at home and care for their child exactly as she wishes [מצודת דוד, ביאור שטיינזלץ]. He agrees that she should not travel to the Tabernacle, noting that women are not obligated to make the pilgrimage, and he backs her decision to bring the boy to serve immediately after he is weaned, despite his very young age [אברבנאל].
At the heart of Elkanah's response is a blessing and a prayer that God will fulfill His promise. This prayer carries multiple layers of meaning. On a practical level, it is a heartfelt request for the child's survival and well-being, asking that the boy will grow up healthy enough for Hannah's vow to actually take place [רלב״ג, ביאור שטיינזלץ, אברבנאל]. Furthermore, since a mother cannot force her child to spend his entire life serving at the Tabernacle, Elkanah prays that God will instill a genuine desire within the boy's own heart to stay there willingly [מצודת דוד].
Beyond the practical hopes for their son, Elkanah's prayer touches upon prophetic promises. Some suggest he is referring to the blessing of Eli the Priest, who foresaw through divine inspiration that God would grant Hannah a child dedicated to Him [רש״י, רד״ק]. Others, however, argue that Eli's blessing was already realized the moment the child was born, making a new prayer for it unnecessary [אברבנאל]. Instead, it is possible that Hannah herself had received a prophetic vision that her son would grow up to be a judge and savior for the Israelites, prompting Elkanah to pray that God would bring her specific vision to life [מלבי״ם].
Alternatively, his blessing might stem from a slight sense of concern. Because Hannah had promised to give the child to God for his entire life, her decision to keep him at home until he was weaned could be seen as a partial step back from an immediate commitment. By praying for the fulfillment of the divine promise, Elkanah approves her delay while expressing hope that this pause will not negatively affect their agreement with God [אהבת יהונתן].
A deeper layer of this story reveals the broader anticipation surrounding the child's birth. During that era, a heavenly voice had proclaimed that a great righteous leader named Samuel was destined to arise. Hearing this, many mothers named their newborn sons Samuel, only to realize as the boys grew up that their actions did not match the prophecy. Through his prayer, Elkanah expresses a hopeful plea that their newborn son is truly the promised righteous leader the heavenly voice had foretold [רש״י, רד״ק, צאינה וראינה, אברבנאל].