Quotation for Berakhot 27:26

(Fol. 14a) Rab said: "Whoever greets his friend before he has prayed is considered as if he had built a heathenish altar, for it is said (Is. 2, 22.) Withdraw yourselves from man whose breath is in his nostrils; for what is he to be esteemed. Do not read Bameh (for what) but read Bamah (a heathen altar)." Samuel explains it, with what right didst thou pay thy regard to him [whom you greeted] and not to God? R. Shesheth raised the following objection: [We have been taught in a Mishnah] "Between the sections he may salute a respectable man and answer," [and the Sh'm'a is before the Eighteen Benedictions and yet one is allowed to salute a respectable man]. R. Abba explained that Rab deals with a man who visits his neighbor for the sole purpose of greeting him before he has prayed [therefore it is wrong, but the Mishnah refers to one who happened to meet his neighbor]. R. Jonah in the name of R. Zeira said: "Whoever greets his friend before he has prayed [is considered as if he] has erected a heathen altar." Questioned by his disciples whether he really meant 'a, heathen altar,' he replied: "I meant that 'it is prohibited,'" as R. Ide b. Abin, who said in the name of R. Isaac b. Assian: "It is prohibited to greet a friend and to go out to business before one has prayed, for it is said (Ps. 85, 14.) Righteousness will go before him." Further said R. Ide b. Abin, in the name of R. Isaac b. Assian: "For him who prays first and then goes to his undertakings, the Holy One, praised be He! will fulfill his desires, for it is said (Ib.) Righteousness will go before him, and will (level) the way by its steps."