It is narrated from Sayyiduna Ibn Abbas (may Allah be pleased with them both) regarding the one who bequeaths a fifth, that he is better than the one who bequeaths a quarter, and the one who bequeaths a quarter is better than the one who bequeaths a third.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الوصايا / 12575