It is narrated from al-Ayzar (may Allah have mercy on him) that Ibn Abbas (may Allah be pleased with them both) was asked about a man who points with his finger while supplicating, and Ibn Abbas (may Allah be pleased with them both) said: Doing so is ikhlas (sincerity).
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 2794