Syriac

pšṭ - to stretch out; to extend; to stretch (LSyr. 611, SL 1258)

PNWS

*pšṭ - to spread, to stretch; to strip off, to separate (EDA I)

May be related to Arb. bsṭ ‘to spread, to expand with an irregular mutation of labials in Arb. (Kogan 2015:477).