Musannaf Ibn Abi Shayba 3:602

Ibn Fudayl narrated to us, from Abdullah ibn Abd al-Rahman, from Salim ibn Abi al-Ja’d, from Salman al-Farisi, who said: "Prayer is a measure. Whoever fulfills it completely, Allah will fulfill [his reward] completely. And you already know what Allah said regarding the measure: 'Woe to those who give less [than due].'"