וַיִּשְׁלַ֣ח פַּרְעֹ֔ה וְהִנֵּ֗ה לֹא־מֵ֛ת מִמִּקְנֵ֥ה יִשְׂרָאֵ֖ל עַד־אֶחָ֑ד וַיִּכְבַּד֙ לֵ֣ב פַּרְעֹ֔ה וְלֹ֥א שִׁלַּ֖ח אֶת־הָעָֽם׃ (פ)
Entonces Faraón envió, y he aquí que del ganado de los hijos de Israel no había muerto uno. Mas el corazón de Faraón se agravó, y no dejó ir al pueblo.
Chizkuni
וישלח פרעה והנה לא מת, “Pharaoh dispatched people to check on the livestock of the Israelites, and not a single one had died.” The reason for this was Moses’ prediction in verse 4 that G-d will make this distinction between Egyptian and Israelite owned beasts.
Chizkuni
ויכבד לבו; “but his heart remained obstinate;” he did not ask Moses to pray, as the dead beasts could not be brought back to life. The beasts that had survived did not need to be prayed for.