Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) said: Hold to the first row, and within it hold to the right side, and beware of forming a row between the pillars.
Al-Tabarani recorded it in al-Mu'jam al-Awsat and al-Mu'jam al-Kabir. Its chain contains a narrator, Isma'il bin Muslim al-Makki, who is da'if (weak).
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الصلاة / 2513