Swami Dayanand Saraswati Commentary : The four Vedas, which are the teaching of the Supreme Lord, eternal, and truthful, are called ‘Books of Knowledge’.
In Hindi:
महर्षि दयानन्द व्याख्या : जो ईश्वरोक्त सनातन, सत्य विद्यामय चार वेद हैं, उनको 'विद्यापुस्तक' कहते हैं ।